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Biofilms are widely recognized as a prominent mode of microbial growth and strategy of antimicrobial tolerance in many environments. Characteristics that are often overlooked in biofilm investigations include the examination of metabolic pathways as the assumption might be that interference with central pathways such as glycolysis would only reduce growth and thus not be meaningful. Using the Keio collection of Escherichia coli mutants, we investigated the influence of biofilm formation and planktonic growth in full-strength and diluted Luria–Bertani (LB) broths using strains with a disruption of glycolysis (Δpgi), the Entner–Doudoroff pathway (Δedd), or the pentose phosphate pathway (Δgnd). Unexpectedly, in contrast to the E. coli Keio parent strain (BW25113), planktonic growth was enhanced in full strength and diluted LB broths in the metabolic mutants. Using a microtiter biofilm assay, the E. coli parent strain showed the highest crystal violet staining. However, when analyzed by culture assays, there was an increase in biofilm populations in the mutants in comparison to the parent strain. Fluorescence microscopy showed differences in colonization patterns in the strains. Given the availability of mutant collections in many model organisms, similar metabolic studies are warranted for biofilms, given their importance in nature. [ABSTRACT FROM AUTHOR]

Bacteria growing as surface-adherent biofilms are better able to withstand chemical and physical stresses than their unattached, planktonic counterparts. Using transcriptional profiling and quantitative PCR, we observed a previously uncharacterized gene, yjfO to be upregulated during Escherichia coli MG1655 biofilm growth in a chemostat on serine-limited defined medium. A yjfQ mutant, developed through targeted-insertion mutagenesis, and a yjfQ-complemented strain, were obtained for further characterization. While bacterial surface colonization levels (c.f.u. [cm.sup.-2]) were similar in all three strains, the mutant strain exhibited reduced microcolony formation when observed in flow cells, and greatly enhanced flagellar motility on soft (0.3%) agar. Complementation of yjfO restored microcolony formation and flagellar motility to wild-type levels. Cell surface hydrophobicity and twitching motility were unaffected by the presence or absence of yjfO. In contrast to the parent strain, biofilms from the mutant strain were less able to resist acid and peroxide stresses. yjfO had no significant effect on E. coli biofilm susceptibility to alkali or heat stress. Planktonic cultures from all three strains showed similar responses to these stresses. Regardless of the presence of yjfQ, planktonic E. coli withstood alkali stress better than biofilm populations. Complementation of yjfO restored viability following exposure to peroxide stress, but did not restore acid resistance. Based on its influence on biofilm maturation and stress response, and effects on motility, we propose renaming the uncharacterized gene, yjfO, as bsmA (biofilm stress and motility). DOI 10.1099/mic.0.031468-0

More than 40 calcite-precipitation experiments were performed under sterile conditions in order to investigate the origins of 25-300 nm spherical-, rod-, and ovoid-shaped objects that have been widely interpreted as evidence of nanometer-scale life (i.e., nannobacteria). Individual experiments included the addition of soluble organic compounds, common species of eubacteria, or phage-induced eubacterial lysates. These experiments indicate that many of the nanometer-scale objects have inorganic or nonnannobacterial origins. In the precipitation experiments, calcite formed euhedral crystals 50-800 nm in diameter and smaller (< 50 nm) anhedral or rounded particles or protocrystals. The small anhedral or rounded solids resembled nannobacteria. The relative amount of anhedral or rounded calcite was greatest in experiments with a dissolved organic component. These controlled experiments are in accord with observations that rounded nanometerscale objects are more common in minerals formed in organic-rich environments. Bacterial fragments occur as rounded to irregularly shaped particles that included cell-wall fragments, expulsed cytoplasm, and relict capsules that also closely resembled nannobacteria. Acid etching of the large euhedral crystals produced in the precipitation experiments also resulted in the formation of nanometer-scale features that resembled nannobacteria in natural carbonates. The shapes of the etching artifacts vary as a function of the strength of the acid and the duration of etching. Much caution is advisable in interpreting the origin of rounded features < 50 nm.

Research was conducted to examine the hypothesis that biofilms on indwelling urethral catheters produce quorum-sensing signal molecules in situ and in vitro. The Pseudomonas aeruginosa biofilms produced strongly positive reaction that were generated on catheters. Sections of the catheters from which biofilm had been taken also gave positive responses in the assay. Results along with negative reactions seen in unused catheters reveal that the quorum-sensing signal molecules may have been generated by the biofilm during its development in the catheter.

The effect of the oxidation states on iron binding by the gamma-glutamyl capsule polymer of Bacillus lichensis was discussed. The methodlogy involved anaerobic suspension of lyophilized capsule in ferric acid solution and addition of reducing agent. The solutions were incubated for one week, unbound metal were removed by dialysis and then prepared for trace metal anaylis. Results showed that less Fe2+ was bound than Fe3+. In addition, Fe3+ bound to the anionic bacterial polymers can released by reduction.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2005.12.002 Byline: Robert J.C. McLean (a), Allana K. Welsh (a), Valerie A. Casasanto (b) Keywords: Exobiology; Meteorites Abstract: A slow growing, heat resistant bacterium, identified by 16S rRNA gene sequencing as Microbispora sp., was recovered from the wreckage of the ill-fated space shuttle Columbia (STS-107). As this organism survived disintegration of the space craft, heat of reentry, and impact, it supports the possibility of a natural mechanism for the interplanetary spread of life by meteorites. Author Affiliation: (a) Department of Biology, Texas State University-San Marcos, 601 University Drive, San Marcos, TX 78676, USA (b) Instrumentation Technology Associates Inc., 110 Pickering Way, Suite 100, Exton, PA 19341, USA Article History: Received 16 May 2005; Revised 21 November 2005

Research was conducted to examine the effect of rpoS deletion on Escherichia coli biofilms. It was hypothesized that slow growth is an essential aspect of bacterial physiology within biofilms. Two strains of Escherichia coli and its isogeic derivvative were used to test the hypothesis. Results indicate that deletion of rpoS greatly reduces the ability of E coli to grow in biofilms but has little impact on the growth of planktonic bacteria.

Spacecraft, associated with human spaceflight, is one of the more unusual microbial environments. In contrast to other terrestrial environments, microorganisms within spacecraft are completely isolated from the rest of the biosphere and experience greatly reduced gravity (microgravity) and increased exposure to solar radiation. Microorganisms are introduced to this environment primarily through the microbiomes associated with spacecrew, as well as small numbers of microorganisms inadvertently introduced with supplies and equipment. In short-term studies (< 96 h) conducted during spaceflight, microgravity has been shown to influence the physiology and gene expression of several microorganisms. These studies can be modelled and extended on Earth using modelled microgravity (MMG) devices. Initial MMG studies, using microbial evolution approaches, show the potential for some microorganisms to develop altered phenotypes in response to microgravity, which in some instances persist during their return to full gravity (1 g) conditions. Extended space missions beyond low Earth orbit must consider microbial changes to virulence and antibiotic susceptibility in the context of microgravity-induced changes in the immune responses of spacecrew. As well microbial interactions with structural materials and life support functions must also be considered. In this chapter, we review current literature, focusing on studies conducted with the International Space Station. [ABSTRACT FROM AUTHOR]

Leaf fossils commonly form through authigenic preservation in which the leaf surface is encrusted with a mineral film, typically iron oxides. The exact mechanism of mineral precipitation is unclear because largely hydrophobic leaf surfaces do not readily bind metal ions; however, previous workers have suggested precipitation of minerals in sediment pore space, at the leaf surface by decay-produced CO2, or on the leaf surface by iron-sheathed bacteria. A 3 by 2 experiment was conducted to determine the role of non-iron bacteria in precipitating metal ions and enhancing fossilization potential in leaves of Platanus and Taxodium, two genera common in the Tertiary fossil record. Leaves of Platanus and Taxodium were separated into two groups, one of which was inoculated for 5 days in river water and the other of which consisted of fresh leaves that served as a control. Leaves of these two groups were placed in solutions of iron chloride, silica, and distilled water to determine mineralization potential. Leaves inoculated in river water developed an anionic bacterial biofilm of diverse bacteria, which rapidly adsorbed [Fe.sup.3+] ions to form ferrihydrite. In contrast, leaves with no biofilm did not mineralize, even after weeks in a solution of iron chloride or silica. Decay was arrested in leaves placed in the iron chloride solution but not distilled water, high levels of iron can inhibit microbial metabolism. These results imply that bacterial colonization of leaves during their first 1-2 weeks in a stream environment may be an essential pre-requisite for authigenic preservation and that precipitation of iron by bacterial biofilms enhances leaf preservation potential by inhibiting the process of decay.

We investigated in vitro the potential mutagenic and toxic effects of two clay-based nanoparticles, Cloisite® Na+ (Cloisite) and halloysite; and multi-walled carbon nanotubes (MWCNT), commonly used in the polymer composite industry. Using the Ames test, the three nanoparticles did not have a true mutagenic effect, although growth of Salmonella enterica var. Typhimurium ( S.typhimurium) was diminished at higher nanoparticle concentrations. We investigated the impact of nanoparticles on Escherichia coli and S. typhimurium including oxyR and rpoS mutants, which are susceptible to oxidative stress. The oxyR mutants were inhibited in the presence of nanoparticles, when grown aerobically with light. Toxicity was not observed in the absence of light or during anaerobic growth. E. coli rpoS mutants exhibited some toxicity when cultured with Cloisite and MWCNT only when grown aerobically with light. There was no effect with other nanoparticles, or with S. typhimurium rpoS mutants. MWCNT exhibited a slight toxic effect against Epithelioma papulosum cyprini (EPC) cells only at the highest concentration tested. There was no discernable toxicity to EPC cells caused by the clay nanoparticles. We conclude that clay-based nanoparticles and MWCNT do not exert a mutagenic effect and do not have a general toxic effect across all bacterial species or between prokaryotic and eukaryotic cells. Modest toxicity was only observed in eukaryotic EPC cells against MWCNT at the highest concentration tested. Limited species-specific toxicity to clay based and MWCNT nanoparticles was seen in bacterial strains primarily due to culture conditions and mutations that exacerbate oxidative stress. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 961-968, 2014. [ABSTRACT FROM AUTHOR]

In order to see whether the stringent response was involved in biofilm formation, Escherichia coli DS291 (MG1655), and its isogenic relA spoT derivative were grown for 48 h in a chemostat at dilution rates of 0.025 and 0.25 h[sup –1] under serine limitation. The absence of the stringent response genes relA and spoT had little effect on the planktonic cell concentrations. However, a significant (P < 0.001) reduction in biofilm cell density of the relA spoT mutants was seen at a doubling time of 40 h. At a doubling time of 4 h, differences in biofilm cell density were not significant. Scanning confocal laser microscopy demonstrated the cell densities of microcolonies in the relA spoT mutant to be lower than those in the wild type. Using a microtiter plate assay, we found biofilm formation in relA spoT mutants to be similarly reduced in minimal media but to be enhanced in rich media (Luria–Bertani broth). No significant differences in biofilm formation were observed between wild type and isogenic relA mutants under any growth conditions. Overall, these results suggest that both stringent response genes relA and spoT are important in nutrient-limited biofilms. Key words: biofilm, stringent response, nutrient limitation, microcolony, Escherichia coli.Pour vérifier si la réponse stricte était impliquée dans la formation du biofilm, l'Escherichia coli DS291 (MG1655) et son dérivé isogénique relA spoT ont été cultivés pendant 48 h dans un chémostat à des dilutions de 0,025 et 0,25 h[sup –1] dans des conditions limitées en sérine. L'absence des gènes de la réponse stricte relA et spoT avait peu d'effet sur les concentrations de cellules planctoniques. Par contre, une diminution significative (P < 0,001) de la densité en cellules du biofilm des mutants relA spoT a été observée avec un temps de génération de 40 h. Avec un temps de génération de 4 h, les différences dans la densité cellulaire du biofilm n'étaient pas significatives. La microscopie confocale au laser a révélé que les densités en cellules des microcolonies avec le mutant relA spoT étaient plus basses qu'avec le type sauvage. Lors d'essais faits dans des plaques à microtitration, nous avons observé que la formation du biofilm avec les mutants relA spoT était réduite de la même façon dans des milieux minimaux mais augmentée dans les milieux riches (bouillon Luria–Bertani). Il n'y avait pas de différence significative dans la formation du biofilm entre la souche sauvage et les mutants isogéniques relA dans chacune des conditions de croissance. Globalement, ces résultats suggèrent que les deux gènes de la réponse stricte relA etspoT sont importants dans les biofilms limités en nutriments.Mots clés : biofilm, réponse stricte, limitation en nutriments, microcolonie, Escherichia coli.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Examines the effects of community composition, growth rate and susceptibility of aquifer biofilm bacteria on betadine disinfection. Evaluation on biofilm formation and resistance to iodine disinfectant betadine; Increase in biolfilm population size with increasing species diversity; Influences of community composition, growth rate and betadine concentration on biofilm formation and betadine resistance.