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Microbiologically influenced corrosion (MIC) is a complicated process that happens ubiquitously and quietly in many fields. As a useful nutritional ingredient in microbial culture media, yeast extract (YE) is a routinely added in the MIC field. However, how the YE participated in MIC is not fully clarified. In the present work, the effect of YE on the growth of sulfate reducing prokaryotes (SRP) Desulfovibrio bizertensis SY-1 and corrosion behavior of X70 pipeline steel were studied. It was found that the weight loss of steel coupons in sterile media was doubled when YE was removed from culture media. However, in the SRP assays without YE the number of planktonic cells decreased, but the attachment of bacteria on steel surfaces was enhanced significantly. Besides, the corrosion rate of steel in SRP assays increased fourfold after removing YE from culture media. MIC was not determined for assays with planktonic SRP but only for biofilm assays. The results confirm the effect of YE on D. bizertensis SY-1 growth and also the inhibitory role of YE on MIC., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Finfish aquaculture is a fast-growing primary industry and is increasingly common in coastal ecosystems. Bacterioplankton is ubiquitous in marine environment and respond rapidly to environmental changes. Changes in bacterioplankton community are not well understood in semi-enclosed stratified embayments. This study aims to examine aquaculture effects in the composition and functional profiles of the bacterioplankton community using amplicon sequencing along a distance gradient from two finfish leases in a marine embayment. Results revealed natural stratification in bacterioplankton associated to NOx, conductivity, salinity, temperature and PO 4 . Among the differentially abundant bacteria in leases, we found members associated with nutrient enrichment and aquaculture activities. Abundant predicted functions near leases were assigned to organic matter degradation, fermentation, and antibiotic resistance. This study provides a first effort to describe changes in the bacterioplankton community composition and function due to finfish aquaculture in a semi-enclosed and highly stratified embayment with a significant freshwater input., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The aim of the present work was to study and compare the effect of growth temperature (20, 30, and 37°C) and surface type (stainless steel and polycarbonate) on the production of virulence factors, such as proteases and siderophores, and the risk of surface contamination associated with Pseudomonas aeruginosa biofilm and planktonic cells. The increase of growth temperature from 20 to 37°C increased (approximately twofold) the electronegative charge and the hydrophobicity of the P. aeruginosa biofilm cell surface. P. aeruginosa biofilm cell adhesion to stainless steel and polycarbonate was 5- and 1.5-fold higher than their planktonic counterparts at 20 and 30°C, respectively. The increase of growth temperature from 20 to 37°C increased the production of proteases (twofold) and siderophores (twofold) and the cytotoxicity (up to 30-fold) against the HeLa cell line in the supernatants of P. aeruginosa planktonic and biofilm cultures. This study also highlighted that biofilm and planktonic P. aeruginosa cells exhibited distinct physiological properties with respect to the production of virulence factors and the cytotoxicity against the Hela cell line. Therefore, effective disinfection procedures should be adapted to inactivate bacteria detached from biofilms.

Marine aquaculture areas are facing stressed environmental challenges, especially the degradation of coastal ecosystems. Here a coordinated time-series study was used to investigate the coastal bacterioplankton biodiversity dynamics of the Yellow Sea, China. Bacterial 16S rRNA gene sequencing revealed a temporal pattern of decreasing of diversity in summer. Functional prediction indicated that metabolic pathways related to the adenosine triphosphate (ATP)-binding cassette transporters and other membrane transporters were significantly enriched in May, while the genetic information processing category was most abundant in March. The May microbiomes showed most significant positive correlation with phosphate concentration, while the August and November microbiomes correlated with temperature and chemical oxygen demand (COD) most, and the March microbiomes showed significant correlation with Cu 2+ level, pH and salinity. The correlations between representative bacteria and environmental parameters revealed in this study may provide insights into the potential influences of human aquaculture activities, on the biodiversity of coastal bacterioplankton., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: The global threat of antimicrobial resistance especially due to the bacterial biofilms has engaged researchers in the search of new treatment modalities. Antimicrobial photodynamic inactivation (aPDI) is one of the alternative treatment modalities which kills bacteria by generating endogenous reactive oxygen species (ROS). In this work authors evaluated the antibacterial and antibiofilm efficacy of rose Bengal (RB) conjugated to CNT against E. coli., Methods: The interaction of anionic dye to the CNT was studied using UV-vis spectroscopy, HRTEM, FTIR and spectrofluorometry. Phototoxicity of RBCNT conjugate against E. coli was studied using a green light of 50 mW and radiant exposure of 1674.7 J/ cm 2 for 10 min. The antibiofilm activity and mechanism of action of RBCNT conjugate in presence of light was evaluated., Results: The loading and encapsulation was found to be 15.46 ± 1.05 and 61.85 ± 4.23% respectively. The photodynamic inactivation of planktonic cells of E. coli was found to 5.46 and 3.56 log 10 CFU/ml reduction on treatment with RBCNT and RB respectively. The conjugate also exhibited efficient and enhanced antibiofilm activity against E. coli. The study of mechanism of action has confirmed cell membrane and DNA damage were the two main targets of aPDI., Conclusion: This report has concluded the efficient photodynamic inactivation occurred in Gram negative bacteria E. coli due to the increased production of ROS inside the bacterial cells. Hence, the newly synthesized RBCNT conjugate can be efficiently utilized to control infections caused by E. coli., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Despite the high success rate of endodontic treatment, failure may occur in some cases. In this case, Enterococcus faecalis is the most common species in endodontic treatment failure and post-treatment apical periodontitis. Therefore, a new adjunctive strategy is needed for the prevention of endodontic infections due to E. faecalis. The aim of the present study was to compare the antimicrobial and anti-biofilm activities of different common photosensitizers (PSs) for use in antimicrobial photodynamic therapy (aPDT) against E. faecalis., Materials and Methods: E. faecalis strain ATCC 29212 was used as the tested strain and methylene blue (MB), toluidine blue O (TBO), indocyanine green (ICG), and curcumin (CUR) were used as PSs. Irradiation was carried out using diode laser and light emitting diode (LED) at wavelengths related to the above PSs. Then, antimicrobial and anti-biofilm activities were measured using the microbial viability assay and crystal violet test, respectively., Results: aPDT with using the above PSs significantly decreased the CFU/mL count of E. faecalis compared to the control group (P < 0.05). The killing percentage of E. faecalis via PS mediated aPDT was 99.6%, 98.2%, 85.1%, and 65.0% for CUR, ICG, TBO, and MB, respectively. aPDT using the above PSs significantly decreased the biofilm formation ability of E. faecalis compared to the control group (P < 0.05). The biofilm reduction percentage of the PSs was 68.4%, 62.9%, 59.0%, and 47.6% for CUR, ICG, TBO, and MB, respectively., Conclusion: CUR and ICG mediated aPDT exhibited considerably more antimicrobial activity than other PSs, while TBO and MB demonstrated weaker anti-biofilm effects against E. faecalis compared to other PSs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The direct inactivation effects of an atmospheric pressure direct current (DC) air plasma against planktonic Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in aqueous solution are investigated in vitro. Upon plasma treatment, extensively analyses on cell culturability, metabolic capacity, membrane integrity, surface morphology, cellular proteins, nucleic acids and intracellular reactive oxygen species (ROS) for both bacterial species were carried out and significant antimicrobial effects observed. Compared with the cellular culturability, a sub-lethal viable but non-culturable (VBNC) state was induced while more S. aureus entered this state than E. coli. Damaged bacterial outer structures were observed and the total concentrations of cellular protein and nucleic acid decreased for both bacteria after plasma treatment. The plasma-induced aqueous reactive species (RS) and intracellular ROS might produce detrimental effects to the bacteria, while S. aureus was less susceptible to the discharge after a 20-min exposure compared to E. coli., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Electron transfer is a rate-limiting step in microbiologically influenced corrosion (MIC) caused by microbes that utilize extracellular electrons. Cross-cell wall electron transfer is necessary to transport the electrons released from extracellular iron oxidation into the cytoplasm of cells. Electron transfer mediators were found to accelerate the MIC caused by sulfate reducing bacteria. However, there is no publication in the literature showing the effect of electron transfer mediators on MIC caused by nitrate reducing bacteria (NRB). This work demonstrated that the corrosion of anaerobic Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was enhanced by two electron transfer mediators, riboflavin and flavin adenine dinucleotide (FAD) separately during a 7-day incubation period. The addition of either 10ppm (w/w) (26.6μM) riboflavin or 10ppm (12.7μM) FAD did not increase planktonic cell counts, but they increased the maximum pit depth on carbon steel coupons considerably from 17.5μm to 24.4μm and 25.0μm, respectively. Riboflavin and FAD also increased the specific weight loss of carbon steel from 2.06mg/cm 2 to 2.34mg/cm 2 and 2.61mg/cm 2 , respectively. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization curves all corroborated the pitting and weight loss data., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Aims: To identify, isolate, and characterize a lytic bacteriophage against the multiple-drug resistant clinical strain of Pseudomonas aeruginosa-2995 and to determine the phage efficacy against the bacterial planktonic cells and the biofilm., Main Methods: Wastewater was used to isolate a bacteriophage. The phage was characterized with Transmission electron microscopy (TEM). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) was used to identify the expressed proteins. Bacteria were cultured in both suspension and biofilm to check and compare their susceptibility to phage lytic action. The activity of the phage (determined as AZ1) was determined against P. aeruginosa-2995 in both planktonic cells and the biofilm., Key Findings: A bacteriophage, designated as AZ1, was isolated from waste water showing a narrow host range. AZ1 was characterized by TEM and could be identified as an isolate in the family Siphoviridae [order Caudovirals]. Seventeen structural proteins ranging from about 12 to 110kDa were found through SDS-PAGE analysis. Its genome was confirmed as dsDNA with a length of approx. 50kb. The log-phase growth of P. aeruginosa-2995 was significantly reduced after treatment with AZ1 (4.50×10 8 to 2.1×10 3 CFU/ml) as compared to control. Furthermore, phage AZ1 significantly reduced 48h old biofilm biomass about 3-fold as compared to control., Significance: Pseudomonas aeruginosa is a ubiquitous free-living opportunistic human pathogen characterized by high antibiotic tolerance and tendency for biofilm formation. The phage, identified in this study, AZ1, showed promising activity in the destruction of both planktonic cells and biofilm of P. aeruginosa-2995. However, complete eradication may require a combination of phages., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Bacterial biofilms show high tolerance towards antibiotics and are a significant problem in clinical settings where they are a primary cause of chronic infections. Novel therapeutic strategies are needed to improve anti-biofilm efficacy and support reduction in antibiotic use. Treatment with exogenous nitric oxide (NO) has been shown to modulate bacterial signaling and metabolic processes that render biofilms more susceptible to antibiotics. We previously reported on cephalosporin-3'-diazeniumdiolates (C3Ds) as NO-donor prodrugs designed to selectively deliver NO to bacterial infection sites following reaction with β-lactamases. With structures based on cephalosporins, C3Ds could, in principal, also be triggered to release NO following β-lactam cleavage mediated by transpeptidases/penicillin-binding proteins (PBPs), the antibacterial target of cephalosporin antibiotics. Transpeptidase-reactive C3Ds could potentially show both NO-mediated anti-biofilm properties and intrinsic (β-lactam-mediated) antibacterial effects. This dual-activity concept was explored using Streptococcus pneumoniae, a species that lacks β-lactamases but relies on transpeptidases for cell-wall synthesis. Treatment with PYRRO-C3D (a representative C3D containing the diazeniumdiolate NO donor PYRRO-NO) was found to significantly reduce viability of planktonic and biofilm pneumococci, demonstrating that C3Ds can elicit direct, cephalosporin-like antibacterial activity in the absence of β-lactamases. While NO release from PYRRO-C3D in the presence of pneumococci was confirmed, the anti-pneumococcal action of the compound was shown to arise exclusively from the β-lactam component and not through NO-mediated effects. The compound showed similar potency to amoxicillin against S. pneumoniae biofilms and greater efficacy than azithromycin, highlighting the potential of C3Ds as new agents for treating pneumococcal infections., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The dynamics and composition of the bacterial community in the coastal waters of Kuwait are poorly understood. In this study, the spatial-temporal variations in the bacterial composition in the surface water along the Kuwaiti coast was examined by 16S rRNA denaturing gradient gel electrophoresis (DGGE) fingerprinting and phylogeny analyses. The sampling sites were Kuwait Bay, Al-Sabbiya (north of the bay) and Al-Khairan (to the south). The bacterial composition was more variable in the summer for all sites. A cluster analysis of the DGGE fingerprint revealed two main clusters, indicating a temporal similarity between sites. Kuwait Bay and Al-Khairan were more similar to each other than to Al-Sabbiya. The bacterial community composition exhibited distinctive spatial variations, with more diversity at Al-Khairan and less diversity at Al-Sabbiya. At all sites, the dominant bacteria were Alphaproteobacteria, in particular Rhodobacteraceae, followed by Alteromonadaceae (Gammaproteobacteria) and Bacteroidetes., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In the microbiologically influenced corrosion (MIC) caused by sulfate reducing bacteria (SRB), iron oxidation happens outside sessile cells while the utilization of the electrons released by the oxidation process for sulfate reduction occurs in the SRB cytoplasm. Thus, cross-cell wall electron transfer is needed. It can only be achieved by electrogenic biofilms. This work hypothesized that the electron transfer is a bottleneck in MIC by SRB. To prove this, MIC tests were carried out using 304 stainless steel coupons covered with the Desulfovibrio vulgaris (ATCC 7757) biofilm in the ATCC 1249 medium. It was found that both riboflavin and flavin adenine dinucleotide (FAD), two common electron mediators that enhance electron transfer, accelerated pitting corrosion and weight loss on the coupons when 10ppm (w/w) of either of them was added to the culture medium in 7-day anaerobic lab tests. This finding has important implications in MIC forensics and biofilm synergy in MIC that causes billions of dollars of damages to the US industry each year., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The biogeochemistry of a tropical shoal bay (Melville Bay, Australia) impacted by the effluent release, precipitation, and deposition of hydrotalcite from an alumina refinery was studied in both wet and dry seasons. Within the deposition zone, sulfate reduction dominated benthic carbon cycling accounting for ≈100% of total microbial activity, with rates greater than those measured in most other marine sediments. These rapid rates of anoxic metabolism resulted in high rates of sulfide and ammonium production and low C:S ratios, implying significant preservation of S in stable sulfide minerals. Rates of total microbial activity were significantly less in control sediments of equivalent grain size, where sulfate reduction accounted for ≈50% of total benthic metabolism. Rates of planktonic carbon cycling overlying the deposition zone were also greater than those measured in the control areas of southern Melville Bay. At the sediment surface, productive algal and cyanobacterial mats helped stabilize the sediment surface and oxidize sulfide to sulfate to maintain a fully oxygenated water-column overlying the impacted zone. The mats utilized a significant fraction of dissolved inorganic N and P released from the sea bed; some nutrients escaped to the water-column such that benthic regeneration of NH₄+ and PO₄³⁻ accounted for 100% and 42% of phytoplankton requirements for N and P, respectively. These percentages are high compared to other tropical coastal environments and indicate that benthic nutrient recycling may be a significant factor driving water-column production overlying the deposition zone. With regard to remediation, it is recommended that the sea bed not be disturbed as attempts at removal may result in further environmental problems and would require specific assessment of the proposed removal process., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

We examine what circumstances allow the coexistence of microorganisms following different nutritional strategies, using a mathematical model. This model incorporates four nutritional types commonly found in planktonic ecosystems: (1) heterotrophic bacteria that consume dissolved organic matter and are prey to some of the other organisms; (2) heterotrophic zooflagellates that depend entirely on bacterial prey; (3) phototrophic algae that depend only on light and inorganic nutrients, and (4) mixotrophs that photosynthesize, take up inorganic nutrients, and consume bacterial prey. Mixotrophs are characterized by a parameter representing proportional mixing of phototrophic and heterotrophic nutritional strategies. Varying this parameter, a range of mixotrophic strategies was examined in hypothetical habitats differing in supplies of light, dissolved organic carbon, and dissolved inorganic phosphorous. Mixotrophs expressing a wide range of mixotrophic strategies persisted in model habitats with low phosphorus supply, but only those with a strategy that is mostly autotrophic persisted with high nutrient supply, and then only when light supply was also high. Organisms representing all four nutritional strategies were predicted to coexist in habitats with high phosphorus and light supplies. Coexistence involves predation by zooflagellates and mixotrophs balancing the high competitive ability of bacteria for phosphorus, the partitioning of partially overlapping resources between all populations, and possibly nonequlibrium dynamics. In most habitats, the strategy predicted to maximize the abundance of mixotrophs is to be mostly photosynthetic and supplement nutritional needs by consuming bacteria.

We assessed the temporal variability of nutrients, phytoplankton and bacterioplankton at two sites of different trophic status in New Caledonia's South-West lagoon, a tropical coastal ecosystem. During stable meteorological conditions, Chl.a, bacterial production and nutrient concentrations experience weak but consistent daily variation. Short-term (1-2 week interval) fluctuations of planktonic variables are in the same range as annual variations at both sites. A part of these short term variations is linked to local meteorological events (wind in the main channel, precipitation at the coastal station). Although annual variations are weak compared to short term variations, phytoplankton and bacterioplankton production show consistent temporal patterns, with maxima in December-January and April-May and minima in August. Annual bacterial production represents 21% and 34% of particulate primary production at the oligotrophic and mesotrophic sites, respectively. Mineral nutrient availability indicates that nitrogen is probably the primary limiting factor of phytoplankton throughout the year., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

We studied the composition of archaeal and bacterial communities present in the sediment and plankton of a shallow suboxic-to-anoxic freshwater pond with high organic matter input, as an example of a kind of inland freshwater system widely distributed in forests of temperate regions. Molecular surveys based on small subunit rRNA genes showed a remarkably high diversity of lineages within the Bacteria, with a total of 18 phyla or candidate divisions being detected, in addition to a few highly divergent phylotypes of unknown affiliation. We identified members of the five subdivisions of the Proteobacteria, as well as Acidobacteria, Verrucomicrobia, Planctomycetes, Bacteroidetes, Chlorobi, Actinobacteria, Firmicutes, Chloroflexi, Gemmatimonadetes, Spirochaetes, Fibrobacteres and the candidate divisions OD1, OP11, TM6, WS1, WS6 and Termite Group 1 ("Endobacteria"). Candidate division OD1 and beta-Proteobacteria were dominant in the environmental libraries of plankton and sediment, respectively. Archaea were also very diverse, but only members of the Euryarchaeota, including Methanosarcinales, Methanomicrobiales and some divergent lineages, were identified. The application of various species richness estimators confirmed the highly diverse nature of both plankton and sediment samples. The pond is a microbial-based complex ecosystem mainly fueled by the degradation of allochthonous organic matter that maintains tightly coupled carbon and sulfur cycles.

Vibrio vulnificus, a human and animal pathogen, is present in low numbers in the Mediterranean Sea. Seawater and plankton samples were collected from a marine coastal zone of the Straits of Messina in the Mediterranean Sea (Italy) in order to investigate V. vulnificus as free-living (>0.2 microm) and associated with small (>64 microm) and large plankton (>200 microm) utilizing cultural and molecular techniques. Characteristic colonies, grown on thiosulfate, citrate, bile salts and sucrose agar plates, were identified using a biochemical protocol system. A PCR assay was used to confirm isolates and to directly detect V. vulnificus in environmental concentrated samples. Specific primers were used to target the structural cytotoxin/hemolysin gene and the variable regions of 16S rRNA species-specific for V. vulnificus. In addition, a tri-primer PCR of 16S rRNA was used for the differentiation of V. vulnificus strains. Direct detection in marine samples was more frequent than isolation of culturable forms. All isolates were assigned to V. vulnificus biotype 1, 16S rRNA type B. These results confirm the low incidence of V. vulnificus in Mediterranean coastal waters. The isolation of cultivable forms is limited to the warmest months. 16S rRNA primers were the most sensitive molecular tool as they allowed detection of V. vulnificus in 79.1% of samples. Due to the low incidence of V. vulnificus in the Mediterranean coastal environment, its detection requires a molecular approach. The occurrence of V. vulnificus as plankton-associated confirms the role of plankton as a potential reservoir for this pathogen.