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Compost and phototrophic bacteria are found to be able to degrade trichloroethylene (TCE) and perchloroethylene (PCE). With a TCE dose increase by more than 10 mg/kg, the TCE degradation decreases due to the toxic effect of this pollutant on microbial consortium activity. The addition of compost combined with a liquid culture of phototrophic bacteria (PTB) is experimentally proved to effectively decrease the TCE content in soil and water. [ABSTRACT FROM AUTHOR]

EPR characteristics of transient paramagnetic states photoinduced in isolated reaction centers of Rhodobacter sphaeroides R26 with intact electron transfer have been studied. It was demonstrated that the detected weak triplet state EPR signal belongs to the primary donor molecule and is populated via the conventional mechanism of radical pair S-T mixing. The distortion of the spectral shape of this signal is explained by the triplet quantum yield anisotropy brought about by the short lifetime of precursor radical pairs. The angular dependence of the anisotropy was evaluated. It was shown that the spectral shape of the triplet state of photosystem II reaction center observed in the case of singly-reduced primary quinone acceptor can also be described by the anisotropic quantum yield of the triplet, with practically the same angular dependence. These properties confirm the conclusions on the mechanism of photoinduced electron transfer in photosystem II, made in previous publications. The peculiarities in the functioning of photosystem II reaction centers are probably determined by strict limitations on the triplet state generation. [ABSTRACT FROM AUTHOR]

The physicochemical properties, species composition, and vertical distribution of microorganisms in the water column, shoreline microbial mat, and small shoreline mud volcanoes of the stratified soda Lake Doroninskoe were investigated in September 2007. The lake is located in the Transbaikal region, in the permafrost zone (51°25′N; 112°28′E). The maximal depth of the contemporary lake is about 6 m, the pH value of the water is 9.72, and the water mineralization in the near-bottom horizon is 32.3 g l−1. In summer, the surface oxygen-containing horizon of the water column becomes demineralized to 26.5 g l−1; at a depth of 3.5–4.0 m, an abrupt transition occurs to the aerobic zone containing hydrosulfide (up to 12.56 g l−1). Hydrosulfide was also detected in trace quantities in the upper water horizons. The density stratification of the water column usually ensures stable anaerobic conditions until the freezing period (November and December). The primary production of oxygenic phototrophs reached 176–230 μg l−1. High rates of dark CO2 assimilation (61–240 μg l−1) were detected in the chemocline. Within this zone, an alkaliphilic species of sulfur-oxidizing bacteria of the genus Thioalkalivibrio was detected (104 cells ml−1). Lithoheterotrophic bacteria Halomonas spp., as well as bacteriochlorophyll a-containing aerobic anoxygenic phototrophic bacteria (AAP) Roseinatronobacter sp. capable of thiosulfate oxidation, were isolated from samples collected from the aerobic zone (0–3 m). The water transparency in September was extremely low; therefore, no visible clusters of anoxygenic phototrophic bacteria (APBs) were detected at the boundary of the hydrosulfide layer. However, purple sulfur bacteria which, according to the results of the 16S rRNA gene analysis, belong to the species Thioalkalicoccus limnaeus, Ectothiorhodospira variabilis, “Ect. magna,” and Ect. shaposhnikovii, were isolated from samples of deep silt sediments. Ect. variabilis and Ect. shaposhnikovii were the major APB species in the shoreline algo-bacterial mat. The halotolerant bacterium Ect. shaposhnikovii, purple nonsulfur bacteria of the genus Rhodobacter, and AAP of Roseococcus sp. were isolated from the samples collected from mud volcanoes. All these species are alkaliphiles, moderate halophiles, or halotolerant microorganisms. [ABSTRACT FROM AUTHOR]

The facultative phototroph Rhodobacter capsulatus takes up the highly toxic oxyanion tellurite when grown under both photosynthetic and respiratory growth conditions. Previous works on Escherichia coli and R. capsulatus suggested that tellurite uptake occurred through a phosphate transporter. Here we present evidences indicating that tellurite enters R. capsulatus cells via a monocarboxylate transport system. Indeed, intracellular accumulation of tellurite was inhibited by the addition of monocarboxylates such as pyruvate, lactate and acetate, but not by dicarboxylates like malate or succinate. Acetate was the strongest tellurite uptake antagonist and this effect was concentration dependent, being already evident at 1 μM acetate. Conversely, tellurite at 100 μM was able to restrict the acetate entry into the cells. Both tellurite and acetate uptakes were energy dependent processes, since they were abolished by the protonophore FCCP and by the respiratory electron transport inhibitor KCN. Interestingly, cells grown on acetate, lactate or pyruvate showed a high level resistance to tellurite, whereas cells grown on malate or succinate proved to be very sensitive to the oxyanion. Taking these data together, we propose that: (a) tellurite enters R. capsulatus cells via an as yet uncharacterized monocarboxylate(s) transporter, (b) competition between acetate and tellurite results in a much higher level of tolerance against the oxyanion and (c) the toxic action of tellurite at the cytosolic level is significantly restricted by preventing tellurite uptake. [ABSTRACT FROM AUTHOR]

A nas gene region from Rhodobacter capsulatus E1F1 containing the putative nasB gene for nitrite reductase was previously cloned. The recombinant His6-NasB protein overproduced in E. coli showed nitrite reductase activity in vitro with both reduced methyl viologen and NADH as electron donors. The apparent Km values for nitrite and NADH were 0.5 mM and 20 μM, respectively, at the pH and temperature optima (pH 9 and 30°C). The optical spectrum showed features that indicate the presence of FAD, iron-sulfur cluster and siroheme as prosthetic groups, and nitrite reductase activity was inhibited by sulfide and iron reagents. These results indicate that the phototrophic bacterium R. capsulatus E1F1 possesses an assimilatory NADH-nitrite reductase similar to that described in non-phototrophic organisms. [ABSTRACT FROM AUTHOR]

Abstract: H2 is considered as the ultimate cleanest energy carrier to be generated from renewable sources. Biohydrogen production is carried out using the enzymes nitrogenase or hydrogenase. The purple sulphur phototrophic bacterium, Thiocapsa roseopersicina BBS contains a nitrogenase and several NiFe hydrogenases. Hydrogenases can be used as fuel cell H2 splitting catalyst and nitrogenase(s) and hydrogenases in biological H2 production. The membrane-associated Hyn and Hup hydrogenases preferentially work in the H2 uptake direction in vivo, the cytoplasmic Hox enzyme is a bidirectional enzyme. Non-nitrogen-fixing conditions, which render Hup and Hyn non-functioning, lead to sustained net hydrogen production via the Hox enzyme. The cumulative H2 production by the apparently constitutive Hox and the inducible nitrogenase may become comparable under appropriate conditions. [Copyright &y& Elsevier]

The structure and production characteristics of microbial communities from the Urinskii alkaline hot spring (Buryat Republic, Russia) have been investigated. A distinctive characteristic of this hot spring is the lack of sulfide in the issuing water. The water temperature near the spring vents ranged from 69 to 38.5°C and pH values ranged from 8.8 to 9.2. The total mineralization of water was less than 0.1 g/liter. Temperature has a profound effect on the species composition and biogeochemical processes occurring in the algal-bacterial mats of the Urinskii hot spring. The maximum diversity of the phototrophic community was observed at the temperatures 40 and 46°C. A total of 12 species of cyanobacteria, 4 species of diatoms, and one species of thermophilic anoxygenic phototrophic bacteria, Chloroflexus aurantiacus, have been isolated from mat samples. At temperatures above 40°C, the filamentous cyanobacterium Phormidium laminosum was predominant; its cell number and biomass concentration comprised 95.1 and 63.9%, respectively. At lower temperatures, the biomass concentrations of the cyanobacterium Oscillatoria limosa and diatoms increased (50.2 and 36.4%, respectively). The cyanobacterium Mastigocladus laminosus, which is normally found in neutral or slightly acidic hydrothermal systems, was detected in microbial communities. As the diatom concentration increases, so does the dry matter concentration in mats, while the content of organic matter decreases. The concentrations of proteins and carbohydrates reached their maximum levels at 45–50°C. The maximum average rate of oxygenic photosynthesis [2.1 g C/(m² day)], chlorophyll a content (343.4 mg/m²), and cell number of phototrophic microorganisms were observed at temperatures from 45 to 50°C. The peak mass of bacterial mats (56.75 g/m²) occurred at a temperature of 65–60°C. The maximum biomass concentration of phototrophs (414.63 × 10−6 g/ml) and the peak rate of anoxygenic photosynthesis [0.42 g C/(m² day)] were observed at a temperature of 35–40°C. [ABSTRACT FROM AUTHOR]

The ability of hydrogenases isolated from Thiocapsa roseopersicina and Lamprobacter modestohalophilus to reduce metal ions and oxidize metals has been studied. Hydrogenases from both phototrophic bacteria oxidized metallic Fe, Cd, Zn and Ni into their ionic forms with simultaneous evolution of molecular hydrogen. The metal oxidation rate decreased in the series Zn>Fe>Cd>Ni and depended on the pH. The presence of methyl viologen in the reaction system accelerated this process. T. roseopersicina and L. modestohalophilus cells and their hydrogenases reduced Ni(II), Pt(IV), Pd(II) or Ru(III) to their metallic forms under H2 atmosphere. These results suggest that metals or metal ions can serve as electron donors or acceptors for hydrogenases from phototrophic bacteria. [ABSTRACT FROM AUTHOR]

The carbon metabolism of representatives of the family Oscillochloridaceae (Oscillochloris trichoides DG6 and the recent isolates Oscillochloris sp. R, KR, and BM) has been studied. Based on data from an inhibitory analysis of autotrophic CO2 assimilation and measurements of the activities of the enzymes involved in this process, it is concluded that, in all Oscillochloris strains, CO2 fixation occurs via the operation of the Calvin cycle. Phosphoenolpyruvate (PEP), which is formed in this cycle, can be involved in the metabolism via the following reaction sequence: PEP (+CO2) å oxalacetate å malate å fumarate å succinate å succinyl-CoA (+CO2) å 2-oxoglutarate. Acetate, utilized as an additional carbon source, can be carboxylated to pyruvate by pyruvate synthase and further involved in the metabolism via the above reaction sequence. Propionyl-CoA synthase and malonyl-CoA reductase, the key enzymes of the 3-hydroxypropionate cycle, have not been detected in Oscillochloris representatives. [ABSTRACT FROM AUTHOR]

We have studied the activity and composition of several geochemically significant physiological groups of bacteria in more than twenty alkaline salt lakes of the north-east Mongolia steppe with water salinity from 3 to 390 g l-1 and pH values ranging from 9.0 to 10.6. Active and diverse microbial communities have been found in most of the lakes. The methanotrophic bacteria were represented by the Type I members. Among the culturable forms of sulfur-oxidizing bacteria obligately chemolithoautotrophic and haloalkaliphilic representatives of the genera Thioalkalimicrobium and Thioalkalivibrio were detected in the sediments at high numbers (up to 106 cells ml-1). The largest population of anaerobic phototrophic bacteria was represented by purple sulfur bacteria of the Ectothiorhodospiraceae family. Salinity was the key factor in determining the activity and the composition of the microbial communities. The most diverse and active prokaryotic populations, including aerobic and anaerobic phototrophic, methanogenic, methanotrophic, sulfur-oxidizing, sulfate-reducing and nitrifying bacteria, were found in lakes with salinity less than 60 g l-1. In hypersaline lakes with a salinity >100 g l-1, the sulfur cycle remained active due to the activity of extremely halotolerant and alkaliphilic sulfur bacteria, while other important functional groups responsible for nitrification and methane oxidation processes were not detected. Overall, the prokaryotic communities of the Mongolian alkaline salt lakes represent an interesting new example of a diverse community of haloalkaliphilic bacteria well adopted to a broad salinity range. [ABSTRACT FROM AUTHOR]

SUMMARY 1. The development of a population of Thiocystis minor (formerly Chromatium minus ) in the deepest, anoxic layers of Moncortès Lake (Lleida, Spain) was studied by means of an in situ , laser particle analyser. Particle size distribution was measured at hourly and monthly time intervals. 2. The population was located between the redoxcline (∼3 m below the mean population depth) and the oxycline (∼6 m above the mean population depth) with a seasonal vertical displacement (SVD) of up to 6 m (from April to October). 3. Diel vertical migration of the population was followed in three field campaigns, when the population was most abundant. The largest vertical displacement was 2.8 m (in 11.5 h) and the fastest vertical displacement was 0.6 m h-1 . Sudden changes in the irradiance reaching the bacterial population were detected by the cells, which moved up or down, rapidly modifying the mean vertical position of the population. 4. There was positive phototaxis with an ascent during the morning and a descent during the afternoon/night. The whole population was active while migrating upwards (towards higher light intensity) or downwards (towards lower redox concentration). [ABSTRACT FROM AUTHOR]

To understand a physiological role of an abundant 34-kDa periplasmic protein in the denitrifying phototroph Rhodobacter sphaeroides f. sp. denitrificans grown in a medium containing malate as the carbon source, the gene for the protein was isolated. The deduced amino acid sequence of the protein had a sequence similarity of 66.2% to that of PstS from Sinorhizobium meliloti. The downstream sequence of the Rhodobacter pstS contained five genes similar to pstCAB and phoUB, and its upstream sequence contained a putative regulatory sequence that is analogous to the Pho box involved in phosphate-limitation-induced gene expression in Escherichia coli. Both the amount of the PstS and the pstS promoter-driven expression of lacZ activity increased about two-fold in response to phosphate limitation. This is the first isolation of pst genes encoding proteins of an ABC phosphate transporter system from phototrophic bacteria. [ABSTRACT FROM PUBLISHER]

The distribution of primary components of the microbial community (autotrophic pico- and nanoplankton, phototrophic bacteria, heterotrophic bacteria, microscopic fungi, heterotrophic flagellates, ciliates and heliozoa) in the water column of Lake Shira, a steppe brackish-water, stratified lake in Khakasia, Siberia (Russia), were assessed in midsummer. Bacterioplankton was the main component of the planktonic microbial community, accounting for 65.3 to 75.7% of the total microbial biomass. The maximum concentration of heterotrophic bacteria were recorded in the monimolimnion of the lake. Autotrophic microorganisms contributed more significantly to the total microbial biomass in the pelagic zone (20.2–26.5%) than in the littoral zone of the lake (8.7–14.9%). First of all, it is caused by development of phototrophic sulphur bacteria at the oxic-anoxic boundary. The concentrations of most aerobic phototrophic and heterotrophic microorganisms were maximal in the upper mixolimnion. Heterotrophic flagellates dominated the protozoan populations. Ciliates were minor component of the planktonic microbial community of the lake. Heterotrophic flagellates were the most diverse group of planktonic eucaryotes in the lake, which represented by 36 species. Facultative and obligate anaerobic flagellates were revealed in the monimolimnion. There were four species of Heliozoa and only three of ciliates in the lake. [ABSTRACT FROM AUTHOR]

Lake Arcas exhibits a thermal stratification from April to October. A sulfide-rich anoxic hypolimnion is then formed between the deeper part of the thermocline and the lake bottom, and high population densities of phototrophic microorganisms are found at the oxic-anoxic interface. Chromatium weissei, a large rod, 8 × 4 μm in size, was the dominant phototrophic bacterium, reaching densities of up to 1.84 × 106 cells ml-1. Other phototrophic sulfur bacteria, such as Amoebobacter cf. purpureus, Thiocapsa sp., and Pelodictyon clathratiforme were also present in the anoxic hypolimnion, but their cell size and population densities were much lower. Net growth rates (0.125 to —0.123 d-1) and frequency of dividing cells, indicated that C. weissei grew most rapidly in the upper part of the phototrophic bacterial layer. The highest growth rates were found during the first half of the stratification period, with a marked decrease in population density as mixing approached. Our results suggest that purple sulfur bacteria in Lake Arcas are light limited, even though they possess okenone, which can efficiently harvest light at the wavelengths penetrating to the chemocline. High rates of carbon photoassimilation by phototrophic bacteria were measured (up to 200 mg C m-3 h-1), but because of the narrow depth range in which anoxygenic photosynthesis occur, bacterial contribution to overall primary production during summer was estimated to be only 12—13%. [ABSTRACT FROM AUTHOR]

The phototrophic bacterium Rhodobacter capsulatus detoxified p-nitrophenol and 4-nitrocatechol. The bacterium tolerated moderate concentrations of p-nitrophenol (up to 0.5 mM) and degraded it under light at an optimal O2 pressure of 20 kPa. The bacterium did not metabolize the xenobiotic in the dark or under strictly anoxic conditions or high O2 pressure. Bacterial growth with acetate in the presence of p-nitrophenol took place with the simultaneous release of nonstoichiometric amounts of 4-nitrocatechol, which can also be degraded by the bacterium. Crude extracts from R. capsulatus produced 4-nitrocatechol from p-nitrophenol upon the addition of NAD(P)H, although at a very low rate. A constitutive catechol 1,2-dioxygenase activity yielding cis,cis-muconate was also detected in crude extracts of R. capsulatus. Further degradation of 4-nitrocatechol included both nitrite- and CO2-releasing steps since: (1) a strain of R. capsulatus (B10) unable to assimilate nitrate and nitrite released nitrite into the medium when grown with p-nitrophenol or 4-nitrocatechol, and the nitrite concentration was stoichiometric with the 4-nitrocatechol degraded, and (2) cultures of R. capsulatus growing microaerobically produced low amounts of 14CO2 from radiolabeled p-nitrophenol. The radioactivity was also incorporated into cellular compounds from cells grown with uniformly labeled 14C- p-nitrophenol. From these results we concluded that the xenobiotic is used as a carbon source by R. capsulatus, but that only the strain able to assimilate nitrite (E1F1) can use p-nitrophenol as a nitrogen source. [ABSTRACT FROM AUTHOR]

A rod-shaped, motile, phototrophic bacterium, strain SiCys, was enriched and isolated from a marine microbial mat, with cysteine as sole substrate. During phototrophic anaerobic growth with cysteine, sulfide was produced as an intermediate, which was subsequently oxidized to sulfate. The molar growth yield with cysteine was 103 g mol, in accordance with complete assimilation of electrons from the carbon and the sulfur moiety into cell material. Growth yields with alanine and serine were proportionally lower. Thiosulfate, sulfide, hydrogen, and several organic compounds were used as electron donors in the light, whereas cystine, sulfite, or elemental sulfur did not support phototrophic anaerobic growth. Aerobic growth in the dark was possible with fructose as substrate. Cultures of strain SiCys were yellowish-brown in color and contained bacteriochlorophyll a, spheroidene, spheroidenone, and OH-spheroidene as major photosynthetic pigments. Taking the morphology, photosynthetic pigments, aerobic growth in the dark, and utilization of sulfide for phototrophic growth into account, strain SiCys was assigned to the genus Rhodovulum (formerly Rhodobacter) and tentatively classified as a strain of R. sulfidophilum. In cell-free extracts in the presence of pyridoxal phosphate, cysteine was converted to pyruvate and sulfide, which is characteristic for cysteine desulfhydrase activity ( l-cystathionine γ-lyase, EC 4.4.1.1). [ABSTRACT FROM AUTHOR]

The gene encoding malate dehydrogenase (MDH) from Chloroflexus aurantiacus was cloned, sequenced, and analyzed. The mdh gene corresponded to a polypeptide of 309 amino acids with a molecular mass of 32,717 Da. The primary structure and the coenzyme-binding domain showed a high degree of similarity to lactate dehydrogenase (LDH), whereas the conserved amino acids that participate in substrate binding were those typical of MDHs. Using PCR techniques, the mdh gene was cloned in the expression vector pET11a, and large amounts of active C. aurantiacus MDH were produced in Escherichia coli after induction with isopropyl β- d-thiogalactoside. The expressed enzyme thus obtained was purified and retained full activity at 55° C. High levels of expression of mdh were also observed when the gene and its flanking sequences were cloned into pUC18/19, indicating that the putative σ promoter sequences found upstream of the C. aurantiacus mdh functioned in E. coli. When these sequences were deleted, the expression in E. coli was reduced dramatically. [ABSTRACT FROM AUTHOR]

The 16S rRNA or rRNA gene sequences of the type strains of 5 species of Rhodobacter, Rhodopseudomonas blastica and Paracoccus denitrificans were determined. The sequence analysis revealed that Rhodobacter species, whose intracytoplasmic membrane systems were characteristically vesicular, composed a sole cluster. Rhodopseudomonas blastica, whose intracytoplasmic membrane system was lamellar, was included in the cluster of Rhodobacter. The phylogenetic co-clustering of these bacteria conformed to their possessing of the identical types of carotenoids. Paracoccus denitrificans, which is nonphototrophic, is a right member of the Rhodobacter cluster. Rhodobacter species, Rhodopseudomonas blastica and Paracoccus denitrificans are apart from the other phototrophic bacteria and have the common deletions of 21 bases at the positions 1258 to 1278 ( Escherichia coli numbering system). It was demonstrated that the morphological character 'intracyto-plasmic membrane structure', that has been regarded as a generic criterion does not reflect the phylogeny in the phototrophic bacteria. The transfer of Rhodopseudomonas blastica to the genus Rhodobacter is proposed. [ABSTRACT FROM AUTHOR]

Synthesis and assembly of leader peptidase of Escherichia coli (signal peptidase I), was studied by heterologous expression of its lep gene in three species of phototrophic purple bacteria. Cell extracts of the recipient species showed neither cross reaction with antibodies against E. coli leader peptidase nor cleavage of the model substrate M13-procoat in vitro. The lep gene was transferred via conjugation using the plasmid expression vector for phototrophic bacteria pJAJ9. Plasmidborne leader peptidase enzyme was identified by immunochemical means. However, extracts of transconjugant cells showed no cleavage function. Trypsin digestion studies revealed that the enzyme was not properly integrated across the host membranes. The data suggest that cleaving enzymes for protein export and/or their assembly pathway in purple bacteria differ from the E. coli type. [ABSTRACT FROM AUTHOR]

Rhodobacter capsulatus strains E1F1 and B10 and Rhodobacter sphaeroides DSM 158 did not use hydroxylamine as nitrogen source for growth but metabolized it mainly through the glutamine synthetase reaction. Hydroxylamine had a high toxicity for cells growing either under phototrophic or dark-aerobic conditions. l-methionine- d,l-sulfoximine partially inhibited hydroxylamine uptake and increased the inhibition time of nitrogenase activity by this nitrogen compound. Nitric oxide was also a powerful inhibitor of nitrogenase in intact cells of R. capsulatus. Since low amounts of NO were produced from hydroxylamine, short-term inhibition of nitrogenase in the presence of this compound could be mediated in vivo by nitric oxide. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides were isolated from the moderate halophilic Ectothiorhodospira shaposhnikovii slight to and Ectothiorhodospira mobilis and from the extremely halophilic Ectothiorhodospira halophila by the hot phenol-water and purified by the phenol-chloroform-petroleum ether methods. The isolated lipopolysaccharides of all three species contained 3-deoxy- d-manno-octulosonic acid and d-glycero- d-mannoheptose indicating the existence of a core. They contained additionally glucose and uronic acids ( E. shaposhnikovii and E. mobilis) or glucose, uronic acids and threonine ( E. halophila). Sodium deoxycholate gel-electrophoresis of the three lipopolysaccharides, each showing only one major band, indicated R-type character of the lipopolysaccharides of the three Ectothiorhodospira species. The lipid A fractions of the lipopolysaccharides from E. shaposhnikovii and E. mobilis represented phosphorylated 'mixed' lipid A types with both 2,3-diamino-2,3-dideoxy- d-glucose and d-glucosamine. The lipid A from E. halophila contained also phosphate and 2,3-diamino-2,3-dideoxy- d-glucose but only traces of d-glucosamine, which would indicated lipid A. The fatty acid spectra were characterized by amide-bound 3-OH-10:0 and 3-OH-12:0 ( E. shaposhnikovii), 3-OH-10:0 ( E. mobilis), or 3-OH-10:0,3-OH-14:0, and 3-oxo-14-0 ( E. halophila). The predominant ester-bound fatty acids were 14:0 and 16:0 ( E. shaposhnikovii and E. mobilis), or 12:0 and 14:1 ( E. halophila). [ABSTRACT FROM AUTHOR]

Chromatium vinosum DSM 185 was grown in continuous culture at a constant dilution rate of 0.071 h with sulfide as the only electron donor. The organism was subjected to conditions ranging from phosphate limitation ( S=2.7 μM and S=1.8 mM) to sulfide limitation ( S=86 μM and S=1.8 mM). At values of S below 7.5 μM the culture was washed out, whereas S above this value resulted in steady states. The saturation constant ( K) for growth on phosphate was estimated to be between 2.6 and 4.1 μM. The specific phosphorus content of the cells increased from 0.30 to 0.85 μmol P mg protein with increasing S. The specific rate of phosphate uptake increased with increasing S, and displayed a non-hyperbolic saturation relationship with respect to the concentration of phosphate in the inflowing medium. Approximation of a hyperbolic saturation function yielded a maximum uptake rate ( V) of 85 nmol P mg protein h, and a saturation constant for uptake ( K) of 0.7 μM. When phosphate was supplied in excess 8.5% of the phosphate taken up by the cells was excreted as organic phosphorus at a specific rate of 8 nmol P mg protein h. [ABSTRACT FROM AUTHOR]

The formation of poly(3-hydroxyalkanoic acid), PHA, by various strains of chemolithotrophic and phototrophic bacteria has been examined. Chemolithotrophic bacteria were grown aerobically under nitrogen-limiting conditions on various aliphatic organic acids. Phototrophic bacteria were grown anaerobically in the light on a nitrogen-rich medium and were subsequently transferred to a nitrogen-free medium containing acetate, propionate, valerate, heptanoate or octanoate as carbon source. All 41 strains investigated in this study were able to synthesize and accumulate PHA. All 11 strains of chemolithotrophic bacteria and all 15 strains belonging to the non-sulfur purple bacteria synthesized a polymer, which contained 3-hydroxy-valerate (3HV) beside 3-hydroxybutyrate (3HB), if the cells were cultivated in the presence of propionate, valerate or heptanoate. Many non-sulfur purple bacteria synthesized copolyesters of 3HB and 3HV even with acetate as carbon source. In contrast, most sulfur purple bacteria did not incorporate 3HV at all. Among 15 strains tested, only Chromatium vinosum strain 1611, C. purpuratum strain BN5500 and Lamprocystis roseopersicina strain 3112 were able to synthesize polyesters containing 3HV with propionate, valerate or heptanoate as carbon source. [ABSTRACT FROM AUTHOR]

Strains of the phototrophic bacteria previously referred to as the ' rhodocyclus gelatinosus-like (RGL)' group were taxonomically studied in comparison with Rhodocyclus species. Cells of the RGL strains were curved rods and motile by means of polar flagella. They contained bacteriochlorophyll a and carotenoids of the spheroidene series. The intracytoplasmic membrane system was absent. Photoorganotropho with various organic compounds as carbon sources was the preferred mode of growth. Aerobic growth at full atmospheric oxygen tension and fermentative growth under anaerobic-dark conditions were also possible. The major cellular fatty acids were palmitoleic acid and palmitic acid, and 3-hydroxylated fatty acids with octanoic acid predominating were also found. Both ubiquinone-8 and rhodoquinone-8 occurred as major quinones. The mol% guanine plus cytosine of the DNAs varied between 59.8 and 60.3. DNA-DNA hybridization studies showed that the RGL strains were highly related to each other but exhibited low levels of the homology to Rhodocyclus species. These data allow the establishment of the RGL group as a new taxon of the purple nonsulfur bacteria, for which the name Rhodoferax fermentans gen. nov., sp. nov. is proposed. [ABSTRACT FROM AUTHOR]

In previous work (Zurdo J, Fernández-Cabrera C and Ramírez JM (1993) Biochem J 290: 531-537), it had been shown that selective extraction of the carotenoid from the light-harvesting protein 2 (LH2) of Rhodobacter capsulatus induced the dissociation of 800-nm absorbing bacteriochlorophyll (Bchl), a 10-nm red shift of 854-nm Bchl, and a decrease of the stability of the protein in detergent solution. In the present study, the Fourier transform Raman and near-infrared circular dichroism spectra of native and carotenoid-depleted LH2 membrane preparations were compared. It was found that while the coupled carbonyls of 854-nm Bchl remained specifically H-bonded to the peptides after carotenoid extraction, the optical activity of the near-infrared electronic transition was significantly altered. Given the excitonic origin of such optical activity, our data suggest that carotenoid extraction elicits a rearrengement of the chromophore cluster and of the associated polypeptide subunits. This implies a significant role of the carotenoid in maintaining the native quaternary structure of the protein, which would be consistent with the observed dissociation of 800-nm Bchl and the loss of solubilized LH2 stability that result from carotenoid removal. There is no evidence for a similar role of the carotenoid in the LH1 protein. [ABSTRACT FROM AUTHOR]

The fatty acid composition and lipid pattern of six strains of heliobacteria have been analysed. The results were fairly uniform for all strains. Phosphatidyl ethanolamine and phosphatidyl glycerol were the dominating lipids found, with the former as the major one. No glycolipids were detected. The general fatty acid pattern was dominated by acids of chain length C to C. An unusually large proportion of monoenoic acids was seen, with up to four positional isomers for each chain length. Methyl branched (iso) fatty acids were present, but not cyclopropyl or hydroxy fatty acids nor fatty alcohols. [ABSTRACT FROM AUTHOR]

We report the presence of a diverse number of Chloroflexus-like organisms in intertidal marine and submerged hypersaline microbial mats using light, infrared fluorescence, and electron microscopy. The intertidal organisms appear morphologically very similar to thermophilic C. aurantiacus while the 2 hypersaline strains are larger and have a more complex ultrastructure composed of chlorosome-bearing internal membranes that appear to arise as invaginations of the cell membrane. By comparing spectroradiometry of microbial mat layers with microscopic observations, we have confirmed that the Chloroflexus-like organisms are major constituents of the hypersaline microbial mat communities. In situ studies on mat layers dominated by Chloroflexus-like organisms showed that sulfide-dependent photoautotrophic activity sustained by near infrared radiation prevailed. Autoradiographic analyses revealed that autotrophy was sustained in the filaments by 750 nm radiation. Three morphologically distinct strains are now maintained in mixed culture. One of these appears to be growing photoautotrophically. [ABSTRACT FROM AUTHOR]

Trehalase, which hydrolyzes the disaccharide trehalose to α- d-glucose was isolated and partially purified (124-fold) from the phototrophic halo-alkaliphilic bacterium Ectothiorhodospira halochloris. The molecular mass was determined to be 480,000 and the isoelectric point pH 5.6. Temperature optimum was found to be 40°C and the pH-optimum 7.8-8.1. In spite of its high K-value of 0.5 M, trehalase of E. halochloris was shown to be specific for trehalose. Trehalase is activated by phosphate which is, however, not involved in the reaction mechanism. The enzyme is activated by the compatible solute betaine and inhibited by salts. In the presence of betaine the K-value is lowered from 0.5 M to 0.16 M; moreover, betaine partially protects enzymatic activity from salt inhibition. The findings indicate that betaine might regulate the trehalose level in the cells by affecting trehalase activity. [ABSTRACT FROM AUTHOR]

Cultures of Chromatium vinosum, devoid of sulfur globules, were supplemented with sulfide and incubated under anoxic conditions in the light. The concentrations of sulfide, polysulfides, thiosulfate, polythionates and elemental sulfur (sulfur rings) were monitored for 3 days by ion-chromatography and reversed-phase HPLC. While sulfide disappeared rapidly, thiosulfate and elemental sulfur (S, S S rings) were formed. After sulfide depletion, the concentration of thiosulfate decreased fairly rapidly, but elemental sulfur was oxidized very slowly to sulfate. Neither polysulfides (S), polythionates (SO, n=4-6), nor other polysulfur compounds could be detected, which is in accordance with the fact that sulfide-grown cells were able to oxidize polysulfide without lag. The nature of the intracellular sulfur globules is discussed. [ABSTRACT FROM AUTHOR]

Export of porin to the outer membrane of the phototrophic purple bacterium Rhodobacter capsulatus was studied with the use of the uncoupler of the electron transport chain, carbonylcyanide- m-chlorophenylhydrazone (CCCP). The agent reversibly blocked the transport of porin across the cytoplasmic membrane. By means of radioactive labeling and immunoprecipitation, porin was found to occur in two forms: (i) the exported form that was extractable from the outer membrane without disrupting the cells, and (ii) a pre-form with a slightly higher apparent molecular mass which accumulated in the cells during the block of the export process. Proteolysis studies revealed that the preform was highly sensitive to added proteases, whereas the exported form was resistant. [ABSTRACT FROM AUTHOR]

Two strains belonging to the genus Ectothiorhodospira were isolated from enrichment cultures inoculated with sulfide-containing samples from the saltern of Trapani. Cells are motile short spirilla with internal stacks of membranes. During sulfide utilization they produce external globules of sulfur that are then completely oxidized to sulfate. These halophilic microorganisms need NaCl concentrations of 11% and 18% and a slightly alkaline pH. They are typical photoautotrophic bacteria, utilizing sulfide, sulfur and, only one of them, thiosulfate as photosynthetic electron donors; growth is stimulated by organic compounds. Neither of the two strains is capable of assimilatory sulfate reduction and neither grows in the dark. Pigments of the two strains are bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series subgroup 1B. Quinones are Q8 and MK8 in a strain and Q8 and MK7 in the other one: the latter situation, with quinone side chains of different lengths, is atypical within phototrophic bacteria. For morphological, physiological and biochemical characters, at least one of these strains clearly stays apart from the six Ectothiorhodospira species described until now. [ABSTRACT FROM AUTHOR]

Nineteen established and one undesignated species of the Rhodospirillaceae were examined for fumarate reduction in connection with their quinone systems. The fumarate reductase activity with reduced methyl viologen (MVH) or FMNH as electron donor was found in membrane (chromatophore) preparations from phototrophically grown cells of all species containing menaquinone (MK) and/or rhodoquinone. The species having ubiquinone as the sole quinone contained no fumarate reductase activity, except some Rhodobacter species showing the FMNH-dependent activity. The MVH-fumarate reductase activity of the MK-type species was not inhibited by Triton X-100 or acetone treatment, suggesting the presence of a fumarate reductase reacting directly with MVH, while such an enzyme was absent in the MK-lacking strains, with few exceptions. The FMNH-fumarate reduction system was abolished by a detergent or acetone extraction in all bacteria but differed much among species with different quinone types as to the response to respiratory inhibitors. These differences in fumarate-reducing properties and quinone systems among the phototrophic bacteria are discussed from evolutionary and taxonomic viewpoints. [ABSTRACT FROM AUTHOR]

The lipopolysaccharide of Ectothiorhodospira vacuolata was obtained by the phenol-water procedure. It contained a 3-O-methyl-hexose, glucose, galacturonic and glucuronic acids. The finding of d-glycero- d-mannoheptose and 2-keto-3-deoxyoctonate (tentatively identified) suggested a core-structure. The lipid fraction of the lipopolysaccharide contained phosphate and both, 2,3-diamino-2,3-dideoxy- d-glucose and d-glucosamine. The major fatty acids were amine-bound 3-OH-10:0 and 3-OH-12:0 and esterbound 14:0 and 16:0 Sodium deoxycholate gel-electrophoresis, showing a single band only, indicated R-type character of the lipopolysaccharide of Ectothiorhodospira vacuolata. [ABSTRACT FROM AUTHOR]

Porin of the outer membrane of Rhodobacter capsulatus St. Louis (ATCC 23782) was isolated and reconstituted into lipid bilayer membranes. The porin was obtained either by the sodium dodecyl sulfate treatment of cell envelopes (SDS-porin) or by saline extraction of whole cells (NaCl-porin). Nanomolar concentrations of both porin preparations resulted in a strong conductance increase of the lipid bilayer membranes by many orders of magnitude. At small protein concentrations the conductance increased in a stepwise fashion, the average single channel conductance being about 0.35 nS in 0.1 M KCl for SDS-porin and NaCl-porin as well. The single channel conductance was a linear function of the specific conductance of the aqueous phase. The results were consistent with the assumption that the porin formed large water-filled transmembrane channels in the membrane. From the average value of the single channel conductance in 0.1 M KCl an effective channel diameter of about 1.5 nm was estimated for both types of porins. [ABSTRACT FROM AUTHOR]

Chromatophores isolated from the marine phototrophic bacterium Rhodobacter sulfidophilus were found to photoreduce NAD with sulfide as the electron donor. The apparent K for sulfide was 370 μM and the optimal pH was 7.0. The rate of NAD photoreduction in chromatophore suspensions with sulfide as the electron donor (about 7-12 μM/h·μmol Bchl) was approximately onetenth the rate of sulfide oxidation in whole cell suspensions. NAD photoreduction was inhibited by rotenone, carbonyl cyanide- m-chlorophenylhydrazone, and antimycin A. Sulfide reduced ubiquinone in the dark when added to anaerobic chromatophore suspensions. These results suggest that electron transport from sulfide to NAD involves an initial dark reduction of ubiquinone followed by reverse electron transport from ubiquinol to NAD mediated by NADH dehydrogenase. [ABSTRACT FROM AUTHOR]

Four strains of the green sulfur bacterium Chlorobium were studied in respect to nitrogen nutrition and nitrogen fixation. All strains grew on ammonia, N, or glutamine as sole nitrogen sources; certain strains also grew on other amino acids. Acetylene-reducing activity was detectable in all strains grown on N or on amino acids (except for glutamine). In N grown Chlorobium thiosulfatophilum strain 8327 1 mM ammonia served to 'switch-off' nitrogenase activity, but the effect of ammonia was much less dramatic in glutamate or limiting ammonia grown cells. The glutamine synthetase inhibitor methionine sulfoximine inhibited ammonia 'switch-off' in all but one strain. Cell extracts of glutamate grown strain 8327 reduced acetylene and required Mg and dithionite, but not Mn, for activity. Partially purified preparations of Rhodospirillum rubrum nitrogenase reductase (iron protein) activating enzyme slightly stimulated acetylene reduction in extracts of strain 8327, but no evidence for an indigenous Chlorobium activating enzyme was obtained. The results suggest that certain Chlorobium strains are fairly versatile in their nitrogen nutrition and that at least in vivo, nitrogenase activity in green bacteria is controlled by ammonia in a fashion similar to that described in nonsulfur purple bacteria and in Chromatium. [ABSTRACT FROM AUTHOR]

The lipopolysaccharides of Rhodobacter sulfidophilus and the two budding species Rhodopseudomonas acidophila and Rhodopseudomonas blastica were isolated and chemically analyzed. The all have a lipid A backbone structure with glucosamine as the only amino sugar. The lipid A's of Rb. sulfidophilus and Rps. blastica contain phosphate, their fatty acids are characterized by ester-linked, unsubstituted 3-OH-10:0 and amide-linked 3-OH-14:0 ( Rb. sulfidophilus) or 3-oxo-14:0 ( Rps. blastica). Lipid A of Rps. acidophila is free of phosphate and contains the rare 3-OH-16:0 fatty acid in amide linkage. The lipopolysaccharides of all three species contain 2-keto-3-deoxy-octonate (KDO) but are devoid of heptoses. Neutral sugars with the exception of glucose are lacking in the lipopolysaccharide of Rb. sulfidophilus. This shows a high galacturonic acid content. The lipopolysaccharides of Rps. acidophila and Rps. blastica have neutral sugar spectra indicative for typical O-chains (rhamnose, mannose, galactose, glucose in both species, and in Rps. blastica additionally 2-O-methyl-6-deoxy-hexose). The taxonomic value of the data is discussed. [ABSTRACT FROM AUTHOR]

The phylogenetically related phototrophic bacteria Rhodospirillum tenue and Rhodocyclus purpureus modulate activity of their glutamine synthetases by adenylylation/deadenylylation. Evidence for covalent modification includes the inhibitory effect of Mg on the activity of glutamine synthetase extracted from cells of either species grown on excess ammonia, and the lack of Mg inhibition of activity of the enzyme isolated from N-( R. tenue) or glutamine ( R. purpureus)-grown cells. In addition, snake venom phosphodiesterase treatment of glutamine synthetase from either species grown on excess ammonia relieved Mg inhibition of the enzyme (as measured via the γ-glutamyl transferase assay), and changed the cation specificity from Mn to Mg (in the biosynthetic assay). [ABSTRACT FROM AUTHOR]

The key enzymes of the glyoxylate cycle, isocitrate lyase and malate synthase, were present in cell-free extracts of the phototrophic, green, thermophilic bacterium Chloroflexus aurantiacus grown with acetate as the sole organic carbon source. The optimum temperature of these enzymes was 40° C, and their specific activities were high enough to account for the observed growth rate. Lower levels of the enzymes were found in extracts from cells grown on a complete medium. Itaconate was shown to inhibit isocitrate lyase from C. aurantiacus 96% at a concentration of 0.25 mM and also had a profound effect on the growth of the organism on acetate, 0.25 mM inhibiting completely. Itaconate also inhibited the growth when added to the complex medium, but in this case much higher concentrations were required. [ABSTRACT FROM AUTHOR]

The lipid compositions of Chlorobium limicola (4 strains) and Chloroflexus aurantiacus (2 strains) have been compared. Both species contained straight-chain, saturated and monosaturated fatty acids as their main fatty acid constituents but the patterns were distinctly different. Chlorobium contained acids of chain-length essentally in the range C−C with n-tetradecanoate, hexadecenoate and n-hexadecanoate predominating. Chloroflexus was characterized by the presence of significant amounts of C and C−C fatty acids not detected in Chlorobium. The latter, on the other hand, contained hydroxylated and cyclopropane-substituted acids not detected in Chloroflexus. Simple wax esters (C−C) were found solely in Chloroflexus and accounted for 2.5-3.0% of the cell dry weight. Their fatty acid constituents ranged from C−C (both saturated and monounsaturated isomers) whereas the alcohols were generally saturated and of chain-length C−C. Waxes in the range C−C accounted for more than 60% of the total. The polar lipid patterns of the two genera also showed marked differences. All strains contained phosphatidyl-glycerol, monogalactosyl diglyceride and sulfoquinovosyldiglyceride. Chlorobium contained in addition cardiolipin, phosphatidylethanolamine, the unidentified 'glycolipid II' and several other unidentified glycolipids, whereas phosphatidyl inositol and a diglycosyl diglyceride were specific for Chloroflexus. The latter lipid contained equimolar amounts of glucose and galactose. Phenol-water extraction yielded material comprising 14% of the dry cell weight for Chlorobium but only 2.5% for Chloroflexus. The Chlorobium material contained two 3-hydroxy fatty acids and several uncommon sugars (not identified). The analytical results were inconclusive regarding occurrence of 2-keto-3-deoxyoctonate. No typical lipopoly-saccharide constituents were found in Chloroflexus. [ABSTRACT FROM AUTHOR]

The vitamin B requirement of Rhodocyclus purpureus 6770, Rhodospirillum tenue 1/67, and Rhodopseudomonas palustris G 53/2 was determined. A wide variety of biogenetic precursors of the vitamin including cobinamide, cobyric acid, cobinic acid and several partially amidated cobyrinic acids showed growth-promoting activity in all three strains. In R. purpureus vitamin B could even be substituted by cobyrinic acid which is the first cobalt-containing precursor of vitamin B so far established. Neither methionine, deoxynucleosides, dimethylbenzimidazole nor increased amounts of cobalt could replace vitamin B as growth factor. Cupribalamin, which is a strong antimetabolite of vitamin B in Escherichia coli 113-3 and Lactobacillus leichmannii ATCC 7830, exhibited only a weak antagonistic effect on growth of R. purpureus and R. tenue. Growth of R. palustris was not inhibited by cupribalamin. The cells of all three strains were shown to contain metal-free corrinoids in addition to cobalt-containing corrinoids. The principal products were identified as 5′-deoxyadenosylcobalamin and hydrogenobalamin, the metal free analogue of vitamin B. The latter does not originate from the vitamin by removal of cobalt but is de novo biosynthesized as could be demonstrated in the case of R. purpureus by a labelling experiment with [C] methyl- l-methionine. [ABSTRACT FROM AUTHOR]

A new phototrophic bacterium was isolated from Jordanian and Kenyan alkaline salt lakes. Cells are rod shaped, 1.5 μm wide and 2-4 μm long, and motile by polar flagella. They divide by binary fission, and possess photosynthetic membranes as lamellar stacks similar to those in the other species of the genus Ectothiorhodospira and the brown colored Rhodospirillum species. The presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series is indicated by the absorption spectra of living cells. Under certain growth conditions the cells form gas vacuoles, may become immotile and float to the top of the culture medium. Sulfide and thiosulfate are used as photosynthetic electron donors. During the oxidation of sulfide to sulfate, elemental sulfur is formed, which is accumulated outside the cells. The organisms are strictly anaerobic, do not require vitamins, are moderately halophilic and need alkaline pH-values for growth. The new species Ectothiorhodospira vacuolata is proposed. [ABSTRACT FROM AUTHOR]

Illumination causes an uptake of oxygen by isolated chromatophores of purple and green bacteria incubated with electron donors. Photooxidase activity of Rhodospirillum rubrum, Chromatium minutissimum, Rhodopseudomonas sphaeroides and Thiocapsa roseopersicina chromatophores is sensitive, and photooxidase activity of Ectothiorhodospira shaposhnikovii and Chlorobium limicola f. thiosulfatophilum is resistant to o-phenanthroline. O uptake by illuminated chromatophores of R. rubrum and C. limicola is stimulated upon the increase of pH of incubation mixture from 5 to 9. Photooxidase activity is also manifested in the intact bacterial cells and not merely in the isolated chromatophores. O uptake by the illuminated R. rubrum cells treated with CN is stimulated by 2-heptyl-4-hydroxyquinoline-N-oxide and a protonophorous uncoupler. The interaction of the photosynthetic and respiratory systems of the electron transfer in the bacterial cells and the probable causes of the strong anaerobic way of life of the green sulfur bacteria are discussed. [ABSTRACT FROM AUTHOR]

An indigenous strain of the purple non-sulphur phototrophic bacterium, Rhodopseudomonas palustris strain B1, was selected for the utilization and treatment of wastewater from a sago-starch-processing decanter. Growth of Strain B1 under anaerobic–light conditions in the carbohydrate-rich effluent was optimized by using 50% (v/v) effluent diluted in a basal minimal mineral medium with the addition to 0.1% (w/v) yeast extract. The optimum level of nitrogen source supplement, ammonium sulphate, was 1.0g/l. Highest cell mass concentration was achieved by using tungsten lamps as the light source with a light intensity of 4 klux. Under these optimal conditions, a maximum biomass of about 2.5g dry cell/l with a pigment content of about 1.1mg carotenoid/g dry weight cell was achieved after 96h of anaerobic cultivation. There was a 77% reduc n the chemical oxygen demand (COD) of the effluent. A cell yield of about 0.59g dry weight cell/g COD was obtained. [ABSTRACT FROM AUTHOR]

The photosynthetic nonsulfur purple bacterium Rhodopseudomonas capsulata strain E1F1 assimilated nitrate or nitrite only in illuminated cultures under anaerobic conditions. The bacterial cells grew aerobically in the dark only when ammonia or other forms of reduced nitrogen were present in the medium. However, nitrate reductase was detected either in light-anaerobic or in dark-aerobic conditions upon addition of nitrate to the media. Changes from light-anaerobic to dark-aerobic conditions and vice versa markedly influenced growth, nitrate uptake and the nitrate reductase levels. Growth on nitrate in the light and nitrate reductase activity were dependent on the presence of molybdenum in the medium whereas the addition of tungstate inhibited both growth and enzyme activity. [ABSTRACT FROM AUTHOR]

Marine salterns are habitats for a large variety of halophilic bacteria. In the anoxic zones, halophilic sulfur bacteria develop mainly at the sediment surface, but only a few of them have so far been isolated from such environments. Among the phototrophic sulfur bacteria that sometimes form purple layers underneath the green cyanobacterial layers, members of the genera Ectothiodhodospira, Chromatium (C. salexigens), Thiocapsa (T. halophila) were isolated. They grow by using sulfide as an electron donor. In the marine salterns, sulfide originates from active sulfate reduction. Among the halophilic sulfate-reducing bacteria, only Desulfovibrio halophilus and Desulfohalobium retbaense have so far been isolated. The ecology and physiology of both kinds of bacteria are discussed in this paper. [ABSTRACT FROM AUTHOR]

Photosynthetic bacteria (PSB) possess versatile metabolic abilities and are widely applied in environmental bioremediation, bioenergy production and agriculture. In this review, we summarize examples of purple non-sulfur bacteria (PNSB) through biofertilization, biostimulation and biocontrol mechanisms to promote plant growth. They include improvement of nutrient acquisition, production of phytohormones, induction of immune system responses, interaction with resident microbial community. It has also been reported that PNSB can produce an endogenous 5-aminolevulinic acid (5-ALA) to alleviate abiotic stress in plants. Under biotic stress, these bacteria can trigger induced systemic resistance (ISR) of plants against pathogens. The nutrient elements in soil are significantly increased by PNSB inoculation, thus improving fertility. We share experiences of researching and developing an elite PNSB inoculant ( Rhodopseudomonas palustris PS3), including strategies for screening and verifying beneficial bacteria as well as the establishment of optimal fermentation and formulation processes for commercialization. The effectiveness of PS3 inoculants for various crops under field conditions, including conventional and organic farming, is presented. We also discuss the underlying plant growth-promoting mechanisms of this bacterium from both microbial and plant viewpoints. This review improves our understanding of the application of PNSB in sustainable crop production and could inspire the development of diverse inoculants to overcome the changes in agricultural environments created by climate change.