Biofilm colonization dynamics and its influence on the corrosion resistance of austenitic UNS S31603 stainless steel exposed to Gulf of Mexico seawater.

Viable bacterial counts, chemical markers, phospholipid fatty acid analysis (PLFA), and Fourier-transformed infrared spectroscopy (FTIR), together with electrochemical methods, were used to study biofilm dynamics and its impact on the corrosion resistance of UNS S31603 stainless steels exposed to the Gulf of Mexico seawater. Biofilms progressively accumulated, peaking on day 20, but finally detached. The extracellular polysaccharide (EPS)/cellular biomass ratio remained low most of the time, but reached its highest level (4.2+/-1.9) also on day 20. Viable bacterial cells reached their highest abundance earlier (approximately 800 CFU/cm2), on day 15. Biofilms were seen covering the stainless steel surfaces heterogeneously and were composed mainly of gram-negative rods, presumably EPS-producing bacteria. Despite the different levels of biofilm biomass and attachment state, field-exposed steel coupons ennobled significantly and showed more active pitting potentials (approximately +500 mVSCE) than on the abiotic control (+650 mVSCE), where no significant ennoblement occurred. These results suggest that the heterogeneous distribution of biofilms, as opposed to the quantity of surface-associated biomass, promotes formation of differential aeration cells, and that this in turn contributes to the ennoblement of these steels.

Why are rod-shaped bacteria rod shaped?

Generally speaking, bacteria grow and divide indefinitely, and as long as the growth conditions are maintained they retain constant dimensions and shapes with little variation. How they do this is a question that I have been considering for three decades. Here, I discuss two hypothetical mechanisms, one for Gram-positive rods and the other for Gram-negative rods. These mechanisms are consistent with what is known, but make some unproven assumptions.

Biomineralization of carbonates by Halomonas eurihalina in solid and liquid media with different salinities: crystal formation sequence.

Carbonate precipitation by 20 strains of the moderately halophilic species Halomonas eurihalina in both solid and liquid media was studied. The influence of salinity and temperature on the quantity and type of crystals precipitated was also investigated. Some strains of H. eurihalina formed crystals in all conditions tested. The mineral phases precipitated were magnesium calcite, aragonite and monohydrocalcite in variable proportions depending on various factors such as the type of growth medium employed and its salinity. Scanning electron microscopy and X-ray dispersive energy microanalysis were used to investigate the crystal formation sequence. The process of biolith formation was sequential. It started with chains or filaments of bacteria, giving way to discs which finally produced spherical forms of approximately 50 microns in diameter. We suggest a mechanism of carbonate crystal formation by H. eurihalina.

Croceibacter atlanticus gen. nov., sp. nov., a novel marine bacterium in the family Flavobacteriaceae.

A bright, saffron-colored marine bacterium HTCC2559T was isolated from the Bermuda Atlantic Time Series station in the western Sargasso Sea, Atlantic Ocean by high throughput culturing methods and characterized by polyphasic approaches. Phenotypic data and phylogenetic analyses showed that the strain is a member of the family Flavobacteriaceae. The strain was gram-negative, non-motile, chemoheterotrophic, strictly aerobic, NaCl-requiring, rod-shaped cells that contain carotenoid pigments but not flexirubin. Several kinds of macromolecules (gelatin, DNA, starch, casein, and elastin) were degraded and carbohydrates, sugar alcohols, organic acids, and amino acids were utilized as sole carbon sources. The dominant fatty acids were branched or hydroxy acids, and 3-OH i17:0, i15:0, i15:1, and i17:1 omega9c were abundant. The DNA G+C content of the strain is 34.8 mol%. Phylogenetic analyses using three treeing algorithms based on 16S rRNA gene sequences revealed that the strain formed a very distinct lineage that is allied closely with several seawater environmental clones in the family Flavobacteriaceae. Therefore, it is proposed from the polyphasic studies that strain HTCC2559T (=ATCC BAA-628T = KCTC 12090T) belongs to a new genus and species named Croceibacter atlanticus gen. nov., sp. nov.

Hymenobacter roseosalivarius gen. nov., sp. nov. from continental Antartica soils and sandstone: bacteria of the Cytophaga/Flavobacterium/Bacteroides line of phylogenetic descent.

Aseptically collected sandstone and soil samples from the antarctic Dry Valleys were inoculated into oligotrophic media and incubated under low light intensities. A total of 41 Gram-negative isolates were obtained with reddish colonies spreading on agar. A sandstone isolate and four soil strains were characterized further. They were nearly identical in morphological, physiological, biochemical and chemotaxonomic properties. They produced large amounts of extracellular polymer and utilized for growth: glucose, saccharose, mannitol, sorbitol, L-aspartate, malate and acetate, but not D-ribose, adonitol, DL-alanine, glutamate, glycolate, lactate or succinate. All strains hydrolyzed gelatin, starch, casein, xylan, Tweens 80 or 60 and dead or living yeast cells, but not cellulose or pectin. Nitrate was not reduced, ethanol was not oxidized and acid was not produced from maltose, mannitol or dulcitol. Ammonia was not produced from peptone. They were strictly aerobic. Major fatty acids were n 16:1 d 9, n 16:1 d 11, n 17:1 d 11, and i 15:0. The strains contained the quinone MK-7 and phosphatidylethanolamine as the main phospholipid. The base ratio ranged from 55 to 61 mol% G+C. A 16S rRNA sequence analysis of strains AA-688 and AA-718 showed these to be identical and to represent a special phylogenetic group within the Cytophaga/Flavobacterium/Bacteroides major line of descent. Three soil strains labeled "Taxeobacter" Txc1, Txg1, and Txo1 (Reichenbach, 1992) belonged to the same group but had lower sequence similarities (<95%). Some of their characteristics were different from those of the antarctic strains: the utilization of C-compounds, hydrolysis of polymers, temperature tolerances, major fatty acids and base ratios. Txc1 and Txg1 may later have to be considered as members of this group, possibly on the species level, while Txo1 could represent a different related genus. It is concluded that the five antarctic strains represent a new genus and species for which the name of Hymenobacter roseosalivarius is proposed. The type strain is AA-718T (DSM 11622T).

Improved production of poly(4-hydroxybutyrate) by Comamonas acidovorans and its freeze-fracture morphology.

Production of poly(4-hydroxybutyrate) [P(4HB)] by Comamonas acidovorans JCM10181 was studied by introducing additional copies of its PHA synthase gene and the beta-ketothiolase gene. A multi-copy-number broad-host-range plasmid vector, pJRD215, was modified to contain the strong hybrid trc promoter in order to express these genes in the wild-type C. acidovorans. Increased copy-number of genes resulted in significant increase in the activities of corresponding enzymes, which could further be increased by inducing with isopropyl-beta-D-thiogalactopyranoside (IPTG), indicating that the expression is under the transcriptional control of the trc promoter. P(4HB) biosynthesis in the recombinant C. acidovorans increased 2-fold to constitute more than 60 wt% of the dry cell weight. No significant decrease in the number-average molecular weights of P(4HB) in the recombinant strain was observed when compared with that of the wild-type. Freeze-fracture electron microscopy of intracellular P(4HB) granules revealed almost similar fracture morphology to the well-known mushroom-type deformation shown by polyhydroxyalkanoates with medium-chain-length monomers.

Ancylobacter dichloromethanicus sp. nov.--a new aerobic facultatively methylotrophic bacterium utilizing dichloromethane.

A novel aerobic facultative methylotroph was isolated from contaminated soil. The organism (strain DM16) is a Gram-negative asporogenous non-motile curved rod multiplying by binary fission. Cells are neutrophilic and mesophilic. This strain utilized dichloromethane, methanol, formate and formaldehyde along with a variety of polycarbon compounds. Strain DM16 employs the ribulosebisphosphate pathway for C1 assimilation. The DNA G+C content is 64.5 mol%. The major ubiquinone is Q-10. The dominant cellular fatty acids are 18:1omega7c (58.6%), cyclo-19:0omega8c (34.8%) and 16:0 (3.2%). Sequencing of the 16S rRNA gene and DNA-DNA hybridization experiments clearly indicated that this methylotroph should be classified as a new species within genus Ancylobacter--Ancylobacter dichloromethanicus sp. nov. with the type strain DM16T (DSM 21507T = VKM B-2484T).

[Cobalt- and chromium-containing inclusions in bacterial cells]. / Kobal't- i khromsoderzhashchie vkliucheniia v kletkakh bakterii.

Bacteria belonging to different taxonomic and physiological groups (members of the genera Pseudomonas, Brevibacterium, Rhodopseudomonas, and Lactococcus) are able to form intracellular cobalt- and chromium-containing magnetic inclusions. The paper deals with the structure and the intracellular localization of these inclusions and their similarity to the known noncrystalline iron-containing magnetic inclusions. The possible biological role of the magnetic inclusions is discussed.

Rapid phenotypic change and diversification of a soil bacterium during 1000 generations of experimental evolution.

Evolutionary pathways open to even relatively simple organisms, such as bacteria, may lead to complex and unpredictable phenotypic changes, both adaptive and non-adaptive. The evolutionary pathways taken by 18 populations of Ralstonia strain TFD41 while they evolved in defined environments for 1000 generations were examined. Twelve populations evolved in liquid media, while six others evolved on agar surfaces. Phenotypic analyses of these derived populations identified some changes that were consistent across all populations and others that differed among them. The evolved populations all exhibited morphological changes in their cell envelopes, including reductions of the capsule in each population and reduced prostheca-like surface structures in most populations. Mean cell length increased in most populations (in one case by more than fourfold), although a few populations evolved shorter cells. Carbon utilization profiles were variable among the evolved populations, but two distinct patterns were correlated with genetic markers introduced at the outset of the experiment. Fatty acid methyl ester composition was less variable across populations, but distinct patterns were correlated with the two physical environments. All 18 populations evolved greatly increased sensitivity to bile salts, and all but one had increased adhesion to sand; both patterns consistent with changes in the outer envelope. This phenotypic diversity contrasts with the fairly uniform increases in competitive fitness observed in all populations. This diversity may represent a set of equally probable adaptive solutions to the selective environment; it may also arise from the chance fixation of non-adaptive mutations that hitchhiked with a more limited set of beneficial mutations.

Isolation and characterization of a marine bacterium capable of utilizing 2-methylphenanthrene.

A marine bacterium isolated from a coastal hydrocarbon-polluted sediment has been described and attributed on the basis of its phenotypic and genotypic characteristics to the genus Sphingomonas sp. This strain was capable of using an alkylated phenanthrene 2-methylphenanthrene, as sole source of carbon and energy. In experiments, 2-methylphenanthrene (0.2 g/l) was added as crystals to the culture medium. After 5 days of aerobic growth at 30 degrees C, 70% was degraded and the complete dissipation occurred after 20 days. Furthermore, the strain could degrade various kinds of polyaromatic compounds, but failed to grow on aliphatic hydrocarbons.

Bacterial filament formation, a defense mechanism against flagellate grazing, is growth rate controlled in bacteria of different phyla.

A facultatively filamentous bacterium was isolated from eutrophic lake water and was identified as Flectobacillus sp. strain MWH38 (a member of the Cytophaga-Flavobacterium-Bacteroides phylum) by comparative 16S rRNA gene sequence analysis. Filament formation by Flectobacillus sp. strain MWH38 and filament formation by Flectobacillus major, the closest known relative of strain MWH38, were studied in chemostat cultures under grazing pressure by the bacterivorous flagellate Ochromonas sp. strain DS and without predation at several growth rates. The results clearly demonstrated that filament formation by the two flectobacilli is growth rate controlled and thus independent of the presence of a predator. However, flagellate grazing positively influenced bacterial growth rates by decreasing bacterial biomass and thus indirectly stimulated filament formation. The results of investigations of cell elongation and filament formation by Comamonas acidovorans PX54 (a member of the beta subclass of the class Proteobacteria) supported the recent proposal that in this species the mechanism of filament formation is growth rate controlled. The finding that the grazing defense mechanism consisting of filament formation is growth rate controlled in the flectobacilli investigated and C. acidovorans PX54 (i.e., in bacteria belonging to divergent evolutionary phyla) may indicate that this mechanism is a phylogenetically widely distributed defense strategy against grazing.

Brucella abortus and its closest phylogenetic relative, Ochrobactrum spp., differ in outer membrane permeability and cationic peptide resistance.

The outer membrane (OM) of the intracellular parasite Brucella abortus is permeable to hydrophobic probes and resistant to destabilization by polycationic peptides and EDTA. The significance of these unusual properties was investigated in a comparative study with the opportunistic pathogens of the genus Ochrobactrum, the closest known Brucella relative. Ochrobactrum spp. OMs were impermeable to hydrophobic probes and sensitive to polymyxin B but resistant to EDTA. These properties were traced to lipopolysaccharide (LPS) because (i) insertion of B. abortus LPS, but not of Escherichia coli LPS, into Ochrobactrum OM increased its permeability; (ii) permeability and polymyxin B binding measured with LPS aggregates paralleled the results with live bacteria; and (iii) the predicted intermediate results were obtained with B. abortus-Ochrobactrum anthropi and E. coli-O. anthropi LPS hybrid aggregates. Although Ochrobactrum was sensitive to polymyxin, self-promoted uptake and bacterial lysis occurred without OM morphological changes, suggesting an unusual OM structural rigidity. Ochrobactrum and B. abortus LPSs showed no differences in phosphate, qualitative fatty acid composition, or acyl chain fluidity. However, Ochrobactrum LPS, but not B. abortus LPS, contained galacturonic acid. B. abortus and Ochrobactrum smooth LPS aggregates had similar size and zeta potential (-12 to -15 mV). Upon saturation with polymyxin, zeta potential became positive (1 mV) for Ochrobactrum smooth LPS while remaining negative (-5 mV) for B. abortus smooth LPS, suggesting hindered access to inner targets. These results show that although Ochrobactrum and Brucella share a basic OM pattern, subtle modifications in LPS core cause markedly different OM properties, possibly reflecting the adaptive evolution of B. abortus to pathogenicity.