Frigoriglobus tundricola gen. nov., sp. nov., a psychrotolerant cellulolytic planctomycete of the family Gemmataceae from a littoral tundra wetland

Planctomycetes of the family Gemmataceae are characterized by large genome sizes and cosmopolitan distribution in freshwater and terrestrial environments but their ecological functions remain poorly understood. In this study, we characterized a novel representative of this family, strain PL17T, which was isolated from a littoral tundra wetland and was capable of growth on xylan and cellulose. Cells of this isolate were represented by pink-pigmented spheres that multiplied by budding and occurred singly or in short chains and aggregates. Strain PL17T was obligately aerobic, mildly acidophilic chemoorganotrophic bacterium, which displayed good tolerance of low temperatures. The major fatty acids were C18:0, C16:1ω5, and βOH-C16:1; the major polar lipid was trimethylornithine. The genome of strain PL17T consisted of a 9.83 Mb chromosome and a 24.69kb plasmid. The G+C contents of the chromosomal and plasmid DNA were 67.4 and 62.3mol%, respectively. Over 8900 potential protein-coding genes were identified in the genome including a putative cellulase that contains a domain from the GH5 family of glycoside hydrolases. The genome of strain PL17T contained one linked and one unlinked rRNA operons with 16S rRNA gene sequences displaying 94.5% similarity to that in Gemmata obscuriglobus UQM2246T. Based on the results of comparative phenotypic, chemotaxonomic and phylogenomic analyses, we propose to classify strain PL17T (= CECT 9407T=VKM B-3467T) as representing a novel genus and species of the family Gemmataceae, Frigoriglobus tundricola gen. nov., sp. nov.

[Vitamin B12-independent strains of Methylophaga marina isolated from Red Sea algae]

Two strains (KM3 and KM5) of halophilic methylobacteria isolated from Red Sea algae do not require vitamin B12 for growth and can use methanol, methylamine, dimethylamine, trimethylamine, dimethyl sulfide, and fructose as sources of carbon and energy. The cells of these strains are gram-negative motile monotrichous (strain KM3) or peritrichous (strain KM5) rods. The strains are strictly aerobic and require Na+ ions but not growth factors for growth. They are oxidase- and catalase-positive and reduce nitrates to nitrites. Both strains can grow in a temperature range of 4 to 37 degrees C (with optimal growth at 29-34 degrees C), at pH between 5.5 and 8.5 (with optimal growth at pH 7.5-8.0), and in a range of salt concentrations between 0.5 and 15% NaCl (with optimal growth at 5-9% NaCl). The phospholipids of these strains are dominated by phosphatidylethanolamine and phosphatidylglycerol and also include phosphatidylcholine, phosphatidylserine, and cardiolipin. The dominant fatty acids are C(16:1omega7c) and C(16:0). The major ubiquinone is Q8. The cells accumulate ectoin, glutamate, and sucrose as intracellular osmoprotectants. The strains implement the 2-keto-3-deoxy-6-phosphogluconate-dependent variant of the ribulose monophosphate pathway. The G+C content of the DNA is 44.4-44.7 mol %. Analysis of the 16S rRNA genes showed that both strains belong to Gammaproteobacteria and have a high degree of homology (99.4%) to Methylophaga marina ATCC 35842T . Based on the data of polyphasic taxonomy, strains KM3 and KM5 are identified as new strains M. marina KM3 (VKM B-2386) and M. marina KM5 (VKM B-2387). The ability of these strains to produce auxins (indole-3-acetic acid) suggests their metabolic association with marine algae.

Sporulating bacteria prefers predation to cannibalism in mixed cultures

Predatory behavior, a property associated with ecosystems, is not commonly observed in microorganisms. However, cannibalistic tendencies have been observed in microorganisms under stress. For example, pure culture of Bacillus subtilis exhibits cannibalism under nutrient limitation. It has been proposed that a fraction of cells in the population produce Spo0A, a regulatory protein that is responsible for delaying sporulation. Cells containing spo0A would produce a killing factor by activating skf operon and an associated pump to export the factor. Cells that do not contain spo0A in the population are lysed. However in addition to the competition among the cells of B. subtilis, these cells also compete with other organisms for the limited nutrients. In this work, we report the cannibalistic behavior of B. subtilis in presence of Escherichia coli under severe nutritional limitation. We demonstrate that B. subtilis lyses cells of E. coli using an antibacterial factor under the regulation of Spo0A. Our experiments also suggest that B. subtilis prefers predation of E. coli to cannibalism in mixed cultures. B. subtilis also demonstrated predation in mixed cultures with other soil microorganisms, such as, Xanthomonas campestris, Pseudomonas aeruginosa and Acinetobactor lwoffi. This may offer B. subtilis a niche to survive in an environment with limited nutrients and under competition from other microorganisms.

Isolation of soil bacteria adapted to degrade humic acid-sorbed phenanthrene

The goal of these studies was to determine how sorption by humic acids affected the bioavailability of polynuclear aromatic hydrocarbons (PAHs) to PAH-degrading microbes. Micellar solutions of humic acid were used as sorbents, and phenanthrene was used as a model PAH. Enrichments from PAH-contaminated soils established with nonsorbed phenanthrene yielded a total of 25 different isolates representing a diversity of bacterial phylotypes. In contrast, only three strains of Burkholderia spp. and one strain each of Delftia sp. and Sphingomonas sp. were isolated from enrichments with humic acid-sorbed phenanthrene (HASP). Using [14C]phenanthrene as a radiotracer, we verified that only HASP isolates were capable of mineralizing HASP, a phenotype hence termed "competence." Competence was an all-or-nothing phenotype: noncompetent strains showed no detectable phenanthrene mineralization in HASP cultures, but levels of phenanthrene mineralization effected by competent strains in HASP and NSP cultures were not significantly different. Levels and rates of phenanthrene mineralization exceeded those predicted to be supported solely by the metabolism of phenanthrene in the aqueous phase of HASP cultures. Thus, competent strains were able to directly access phenanthrene sorbed by the humic acids and did not rely on desorption for substrate uptake. To the best of our knowledge, this is the first report of (i) a selective interaction between aerobic bacteria and humic acid molecules and (ii) differential bioavailability to bacteria of PAHs sorbed to a natural biogeopolymer.

Influence of growth environment on coaggregation between freshwater biofilm bacteria

AIM

To characterize the expression of coaggregation between Blastomonas natatoria 2.1 and Micrococcus luteus 2.13 following growth in liquid culture, on agar and in an artificial biofilm matrix composed of poloxamer hydrogel.

METHODS AND RESULTS

The ability of B. natatoria 2.1 and M. luteus 2.13 to coaggregate with one another was assessed following growth in liquid culture as colonies on agar or within a poloxamer hydrogel matrix. In all these environments a cycle of gain and loss of coaggregation occurred when the two cell types were aged simultaneously, with optimum expression occurring in early stationary phase. Blastomonas natatoria 2.1 cells only coaggregated maximally after entry into stationary phase. Conversely, M. luteus 2.13 cells only coaggregated in exponential phase and early stationary phase and coaggregation ability was lost in late stationary phase. Maximal coaggregation therefore only occurred between the two strains if both were in early stationary phase, when the surface properties of the two cell types were optimal for coaggregation.

CONCLUSION

In addition to occurring between cells grown in liquid culture, coaggregation between aquatic bacteria occurs after growth as a biofilm on agar and in an artificial biofilm matrix in poloxamer. Under all conditions, the B. natatoria 2.1 coaggregation adhesin and complementary receptor on M. luteus 2.13 were only expressed simultaneously during early stationary phase.

Modeling of chlorine effect on floc forming and filamentous micro-organisms of activated sludges

Chlorination is the most economical, non-specific method to control the excessive growth of filamentous micro-organisms causing bulking in activated sludge systems in the treatment of food industrial wastewaters; it was one of the first methods used to control filamentous bulking and is still widely employed. Considering that chlorination affects both floc-forming and filamentous micro-organisms and leaves undesirable disinfection by-products, it is necessary to define the adequate doses to control bulking, minimizing the effect on floc-forming bacteria. In the present work the effect of biomass concentration and type of micro-organism on chlorine decay kinetics was evaluated; the inactivation of either a filamentous (Sphaerotilus natans) or a floc-forming (Acinetobacter anitratus) micro-organism due to chlorination was also analyzed. For chlorine decay assays, the samples were treated in a batch system with sodium hypochlorite ranging between 9.8 and 56.6 mg Cl(2) (gVSS)(-1). Respirometric assays were used to evaluate the effect of chlorine on micro-organisms respiratory activity; in these cases, sodium hypochlorite doses ranged between 2.5 and 18 mgCl(2) (gVSS)(-1).A model that allowed to predict simultaneously chlorine consumption and respiratory activity decay for both micro-organisms as a function of time was proposed. The model includes three coupled differential equations corresponding to respiratory inhibition, readily organic matter oxidation by chlorine and chlorine decay. The rate of chlorine decay depended on both, type and concentration of the micro-organisms in the system. Chlorine consumption rate due to S. natans was 2-4 times faster than A. anitratus. Using the proposed model initial critical chlorine doses (the lowest initial dose that leads to a total inhibition of the respiratory activity) were calculated for both micro-organisms and values of 11.9 mgCl(2) (gVSS)(-1) for S. natans and 4.5 mgCl(2) (gVSS)(-1) for A. anitratus were obtained. These critical doses indicated that in non flocculated pure cultures, floc-former bacteria A. anitratus was more susceptible to chlorine action than S. natans.

Gelidibacter mesophilus sp. nov., a novel marine bacterium in the family Flavobacteriaceae

Two Gram-negative, aerobic, heterotrophic, marine bacteria, isolated from Mediterranean sea water off the coast near Valencia (Spain), were the object of this study. These non-motile, yellow-pigmented, rod-shaped strains have been studied by means of DNA-DNA hybridization, 16S rRNA sequencing and cultural and physiological features. Phylogenetic analysis showed that both strains belong to the phylum Cytophaga-Flavobacterium-Bacteroides, and their closest neighbour is the psychrophilic bacterium Gelidibacter algens. The two strains differ from G. algens in their mesophilic behaviour, hydrolytic pattern and use of different carbon sources. There is 31% DNA-DNA hybridization between the proposed type strain and G. algens, and both isolates show 97.5% 16S rDNA similarity to G. algens. They represent a novel species of the genus Gelidibacter, for which the name Gelidibacter mesophilus sp. nov. is proposed, with strain 2SM29T (= CECT 5103T = DSM 14095T) as the type strain.

A patient with severe acute pancreatitis successfully treated with a new critical care procedure

It has been accepted widely that excessive humoral mediators play important roles in the pathogenesis of organ failure in patients with severe acute pancreatitis (SAP) and that infection of the pancreas due to bacterial translocation (BT) is the most frequent cause of death in SAP. On the other hand, it has been reported that continuous hemodiafiltration (CHDF) removes humoral mediators on hypercytokinemic patients such as those with systemic inflammatory response syndrome. Furthermore, several clinical studies have demonstrated that selective digestive decontamination (SDD) effectively eliminates aerobic Gram-negative bacteria from the intestinal tract and reduces the incidence of septic complications in SAP. Herein we report a case of SAP who was treated successfully with intensive care including CHDF and SDD. Thus, this case report suggests that CHDF aimed at removing causative humoral mediators and SDD for the prevention of BT are useful new tools for the management of SAP.

Probiotic supplementation reduces the risk of bacterial translocation in experimental short bowel syndrome

BACKGROUND/PURPOSE

Probiotics are live organisms that survive passage through the gastrointestinal tract and have beneficial effects on the host. Lactobacillus and Bifidobacterium have been recommended for cholesterol lowering, acute diarrhea, prevention of cancer, or inflammatory bowel disease. On the other hand, after massive bowel resection, bacterial overgrowth is frequent and favors bacterial translocation (BT). The possible beneficial effects of Bifidobacterium lactis (BL) administration on BT in experimental short bowel syndrome (SBS), have not been investigated. The aim of this study was to test the hypothesis that BL administration decreases BT in SBS in animals fed orally.

METHODS

One hundred twenty-eight adult Wistar rats fed orally with standard rat chow and tap water "ad libitum" were maintained in individual metabolic cages for 10 days and divided into 3 groups: control group (n = 71): nonmanipulated animals; RES group (n = 39): 80% gut resection from 10 cm beyond the angle of Treitz to 10 cm above the cecum; RES-PRO group (n = 18): same resection and daily 7.8 x 10(8) CFU B Lactis administration, after orogastric intubation. At the end of the experiment they were killed, and mesenteric lymph nodes (MLN) and peripheral and portal blood specimens were recovered and cultured. Bacterial identification in blood was made by conventional methods, and MLN culture was considered positive with a growth over 100 CFU/g.

RESULTS

Bacterial translocation was detected in 6% of control group rats. The incidence of BT in the RES group was 87% (34 of 39), whereas only 50% (9 of 18) of RES-PRO animals had BT (P <.05). The relative risk reduction (RRR) was 0.43 (95% Cl 0.14 to 0.72), and the number needed to treat (NNT) was 3 (95% Cl 2 to 8). In other words, animals that received BL had the risk of BT reduced by 43% (RRR of 0.43), and of every 3 animals treated, 1 is expected to be free of BT (NNT of 3).

CONCLUSION

Administration of B Lactis reduces the incidence of BT in adult Wistar rats after 80% gut resection.

Effect of oxide formation mechanisms on lead adsorption by biogenic manganese (hydr)oxides, iron (hydr)oxides, and their mixtures

The effects of iron and manganese (hydr)oxide formation processes on the trace metal adsorption properties of these metal (hydr)oxides and their mixtures was investigated by measuring lead adsorption by iron and manganese (hydr)oxides prepared by a variety of methods. Amorphous iron (hydr)oxide formed by fast precipitation at pH 7.5 exhibited greater Pb adsorption (gamma(max) = 50 mmol of Pb/mol of Fe at pH 6.0) than iron (hydr)oxide formed by slow, diffusion-controlled oxidation of Fe(II) at pH 4.5-7.0 or goethite. Biogenic manganese(III/IV) (hydr)oxide prepared by enzymatic oxidation of Mn(II) by the bacterium Leptothrix discophora SS-1 adsorbed five times more Pb (per mole of Mn) than an abiotic manganese (hydr)oxide prepared by oxidation of Mn(II) with permanganate, and 500-5000 times more Pb than pyrolusite oxides (betaMnO2). X-ray crystallography indicated that biogenic manganese (hydr)oxide and iron (hydr)oxide were predominantly amorphous or poorly crystalline and their X-ray diffraction patterns were not significantly affected by the presence of the other (hydr)oxide during formation. When iron and manganese (hydr)oxides were mixed after formation, or for Mn biologically oxidized with iron(III) (hydr)oxide present, observed Pb adsorption was similar to that expected for the mixture based on Langmuir parameters for the individual (hydr)oxides. These results indicate that interactions in iron/manganese (hydr)oxide mixtures related to the formation process and sequence of formation such as site masking, alterations in specific surface area, or changes in crystalline structure either did not occur or had a negligible effect on Pb adsorption by the mixtures.

Mechanism of plant growth promotion by rhizobacteria

Plant growth results from interaction of roots and shoots with the environment. The environment for roots is the soil or planting medium which provide structural support as well as water and nutrients to the plant. Roots also support the growth and functions of a complex of microorganisms that can have a profound effect on the growth anti survival of plants. These microorganisms constitute rhizosphere microflora and can be categorized as deleterious, beneficial, or neutral with respect to root/plant health. Beneficial interactions between roots and microbes do occur in rhizosphere and can be enhanced. Increased plant growth and crop yield can be obtained upon inoculating seeds or roots with certain specific root-colonizing bacteria- 'plant growth promoting rhizobacteria'. In this review, we discuss the mechanisms by which plant growth promoting rhizobacteria may stimulate plant growth.

Idiomarina gen. nov., comprising novel indigenous deep-sea bacteria from the Pacific Ocean, including descriptions of two species, Idiomarina abyssalis sp. nov. and Idiomarina zobellii sp. nov

Two bacterial strains, KMM 227T and 231T, were isolated from seawater samples collected from the north-western Pacific Ocean at a depth of 4000-5000 m and were characterized using polyphasic taxonomy. Both were Gram-negative, psychrotolerant, heterotrophic, aerobic and required NaCl for growth (0.6-15.0%). The temperature for growth was 4-30 degrees C. Both strains were rod-shaped, with a single flagellum. However, strain KMM 231T revealed a single long fimbrium. Cellular fatty acids detected in the isolates were predominantly odd-numbered and iso-branched, with 15 and 17 carbons (ca. 70%). Also present were saturated and monounsaturated straight-chain fatty acids. Results of phylogenetic analyses, employing three tree-making methods, strongly indicated that the two strains formed a distinct lineage within a clade containing the genera Alteromonas, Colwellia and Pseudoalteromonas, in the gamma-Proteobacteria. The two strains shared 16S rDNA sequence similarity of 96.9% and genomic DNA relatedness of 27%; the latter was determined by dot-blot hybridization. The strains were differentiated by the presence of fimbria, production of chitinase, ability to grow on 15% NaCl and BIOLOG profiles. Given the polyphasic evidence accumulated in this study, it is proposed that the two deep-sea isolates be classified in the genus Idiomarina gen. nov., as Idiomarina abyssalis sp. nov. (type strain is KMM 227T) and Idiomarina zobellii sp. nov. (type strain is KMM 231T).

Leptospirillum gen. nov. (ex Markosyan 1972), nom. rev., including Leptospirillum ferrooxidans sp. nov. (ex Markosyan 1972), nom. rev. and Leptospirillum thermoferrooxidans sp. nov. (Golovacheva et al. 1992)

The name Leptospirillum ferrooxidans is not in the Approved Lists of Bacterial Names (1980), nor has it been subsequently validly published. In accordance with the rules of the International Code of Nomenclature of Bacteria, the name Leptospirillum for the genus (gen. nov., nom. rev.) and Leptospirillum ferrooxidans for the species (sp. nov., nom. rev.) is revived here. The type species is Leptospirillum ferrooxidans strain L15T (= DSM 2705T). The second species in the genus is Leptospirillum thermoferrooxidans (Golovacheva et al. 1992) (type strain L-88T; Institute of Microbiology, INMI, Moscow, Russia).

Phylogenetic characterization of a novel radiation-resistant bacterium from irradiated pork: description of Hymenobacter actinosclerus sp. nov

A phylogenetic analysis was performed on a red-pigmented, radiation-resistant, Gram-negative, rod-shaped organism originating from irradiated pork. Comparative 16S rRNA gene sequencing showed the bacterium was a member of the Cytophaga-Flavobacterium-Bacteroides line of descent and represents a new subline within the genus Hymenobacter. A new species, Hymenobacter actinosclerus, is described for this novel radiation-resistant bacterium. The type strain of Hymenobacter actinosclerus is CCUG 39621T.

Pseudoalteromonas peptidolytica sp. nov., a novel marine mussel-thread-degrading bacterium isolated from the Sea of Japan

A new bacterial species belonging to the genus Pseudoalteromonas is described on the basis of phenotypic characterization, and sequence analysis of its 16S rRNA-coding and gyrase B (gyrB) genes. Ten strains, isolated from sea water of Yamato Island, Sea of Japan, were Gram-negative, yellow, motile, polarly flagellated, aerobic, rod-shaped eubacteria and had a G + C content of 42 mol%. Analysis of the 16S rDNA sequence revealed a clear affiliation between these strains and members of the gamma-Proteobacteria. High similarity values were found with members of the genus Pseudoalteromonas and this was supported by fatty acid profiles. The 16S rDNA sequence similarity between strain F12-50-A1T and Pseudoalteromonas piscicida was very high (99.1%). However, molecular characterizations employing small subunit 16S rDNA sequences were at the limits of resolution for the differentiation of species in this genus. As a result, DNA-DNA hybridization and sequence analyses of a more rapidly evolving gyrB gene were performed. Our assertion that this strain represents a distinct bacterial species within the genus Pseudoalteromonas was supported by both of these molecular analyses. Species-specific PCR probes were designed for the gyrB gene and used for the rapid screening of F12-50-A1T-like strains, thereby confirming the species. As these strains cleave complex protein compounds of the Mytilus edulis foot by secreting proteases, the name Pseudoalteromonas peptidolytica sp. nov. is proposed, with strain F12-50-A1T (= MBICC F1250A1T) as the type strain.

Thermobacillus xylanilyticus gen. nov., sp. nov., a new aerobic thermophilic xylan-degrading bacterium isolated from farm soil

An aerobic, thermophilic, xylanolytic, spore-forming bacterium, XETP (T = type strain; P = patent strain), has been isolated from farm soil situated underneath a manure heap in northern France. Strain XETP, which stained negative in the Gram test, occurs as short rods which sometimes form chains. Its spores are ellipsoidal, central to subterminal and occur in swollen sporangia. It grows at temperatures up to 63 degrees C and in the pH range 6.5-8.5. When grown on glucose in optimal conditions, its doubling time was found to be 33 min. CO2 was observed to have a growth-stimulating effect at the start of the culture. In addition to glucose, the isolate utilizes xylose, arabinose, mannose, cellobiose, galactose, maltose, sucrose, xylan and starch. Growth is inhibited by 5% NaCl. The G+C content of strain XETP is 57.5 mol%. The 16S rDNA sequence analysis indicated that strain XETP falls into the radiation of the Bacillus-Lactobacillus-Streptococcus subdivision of the Gram-positive phylum. Its three closest phylogenetic relatives are 'Bacillus viscosus', Paenibacillus curdlanolyticus and Bacillus popilliae with identity values of 91.15, 90.94 and 90.92%, respectively. The major cellular fatty acids are 14-methyl pentadecanoic acid (16:0 iso), hexadecanoic acid (16:0) and 14-methyl hexadecanoic acid (17:0 anteiso). On the basis of 16S rRNA sequence and chemotaxonomic characteristics, the isolate is different enough for it to be considered as a member of a new genus. It is therefore proposed that this isolate represents a new genus and species: Thermobacillus xylanilyticus. Strain XETP, the type strain of Thermobacillus xylanilyticus, has been deposited in the Collection Nationale de Cultures Microbiennes (CNCM I-1017) as a patent strain.

Natural communities of Achromatium oxaliferum comprise genetically, morphologically, and ecologically distinct subpopulations

The diversity and ecology of natural communities of the uncultivated bacterium Achromatium oxaliferum were studied by use of culture-independent approaches. 16S rRNA gene sequences were PCR amplified from DNA extracted from highly purified preparations of cells that were morphologically identified as A. oxaliferum present in freshwater sediments from three locations in northern England (Rydal Water, Jenny Dam, Hell Kettles). Cloning and sequence analysis of the PCR-amplified 16S rRNA genes revealed that multiple related but divergent sequences were routinely obtained from the A. oxaliferum communities present in all the sediments examined. Whole-cell in situ hybridization with combinations of fluorescence-labelled oligonucleotide probes revealed that the divergent sequences recovered from purified A. oxaliferum cells corresponded to genetically distinct Achromatium subpopulations. Analysis of the cell size distribution of the genetically distinct subpopulations demonstrated that each was also morphologically distinct. Furthermore, there was a high degree of endemism in the Achromatium sequences recovered from different sediments; identical sequences were never recovered from different sampling locations. In addition to ecological differences that were apparent between Achromatium communities from different freshwater sediments, the distribution of different subpopulations of Achromatium in relation to sediment redox profiles indicated that the genetically and morphologically distinct organisms that coexisted in a single sediment were also ecologically distinct and were adapted to different redox conditions. This result suggests that Achromatium populations have undergone adaptive radiation and that the divergent Achromatium species occupy different niches in the sediments which they inhabit.

Citromicrobium bathyomarinum, a novel aerobic bacterium isolated from deep-sea hydrothermal vent plume waters that contains photosynthetic pigment-protein complexes

We have taxonomically and phylogenetically characterized a new aerobic bacterial strain (JF-1) that contains photosynthetic pigment-protein complexes and which was recently isolated from black smoker plume waters of the Juan de Fuca Ridge. Strain JF-1 is a gram-negative, yellow-pigmented, motile bacterium that is salt-, pH-, and thermotolerant. These properties are consistent with an oligotrophic adaptation to varied environmental conditions thought to exist around deep-sea hydrothermal vents. The analysis of 16S rDNA sequences revealed that strain JF-1 forms a separate phylogenetic branch between the genus Erythromonas and the Erythromicrobium-Porphyrobacter-Erythrobacter cluster within the alpha subclass of the Proteobacteria. The taxonomic name Citromicrobium bathyomarinum (gen. nov., sp. nov.) is proposed for strain JF-1.

Cell surface analysis techniques: What do cell preparation protocols do to cell surface properties?

Cell surface analysis often requires manipulation of cells prior to examination. The most commonly employed procedures are centrifugation at different speeds, changes of media during washing or final resuspension, desiccation (either air drying for contact angle measurements or freeze-drying for sensitive spectroscopic analysis, such as X-ray photoelectron spectroscopy), and contact with hydrocarbon (hydrophobicity assays). The effects of these procedures on electrophoretic mobility, adhesion to solid substrata, affinity to a number of Sepharose columns, structural integrity, and cell viability were systematically investigated for a range of model organisms, including carbon- and nitrogen-limited Psychrobacter sp. strain SW8 (glycocalyx-bearing cells), Escherichia coli (gram-negative cells without a glycocalyx), and Staphylococcus epidermidis (gram-positive cells without a glycocalyx). All of the cell manipulation procedures severely modified the physicochemical properties of cells, but with each procedure some organisms were more susceptible than others. Considerable disruption of cell surfaces occurred when organisms were placed in contact with a hydrocarbon (hexadecane). The majority of cells became nonculturable after air drying and freeze-drying. Centrifugation at a high speed (15,000 x g) modified many cell surface parameters significantly, although cell viability was considerably affected only in E. coli. The type of washing or resuspension medium had a strong influence on the values of cell surface parameters, particularly when high-salt solutions were compared with low-salt buffers. The values for parameters obtained with different methods that allegedly measure similar cell surface properties did not correlate for most cells. These results demonstrate that the methods used to prepare cells for cell surface analysis need to be critically investigated for each microorganism so that the final results obtained reflect the nature of the in situ microbial cell surface as closely as possible. There is an urgent need for new, reliable, nondestructive, minimally manipulative cell surface analysis techniques that can be used in situ.

Fundibacter jadensis gen. nov., sp. nov., a new slightly halophilic bacterium, isolated from intertidal sediment

A moderately halophilic hydrocarbon-degrading bacterium was isolated from continuous cultures containing a suspension of intertidal sediment from the German North Sea coast with hexadecane as the sole carbon source. On the basis of phenotypic characteristics, fatty acid analysis and 16S rDNA sequence analysis, it was considered to be a new species belonging to a new genus. It is a Gram-negative, aerobic, rod-shaped bacterium, whose cell size varies. It grows at concentrations of 0.5-15% (w/v) NaCl and utilizes a restricted spectrum of carbon sources. The G + C content of the DNA is 63.6 mol%. Comparative 16S rDNA studies show a clear affiliation of this bacterium to the gamma subclass of the class Proteobacteria. Comparison of phylogenetic data indicate that it is most closely related to Marinobacter hydrocarbonoclasticus (88.9% similarity in 16S rRNA gene sequence). Since it is impossible to find a sufficiently closely related species, we propose the name Fundibacter jadensis gen. nov., sp. nov. for the bacteria. The type strain is T9T (= DSM 12178T).

Roseovarius tolerans gen. nov., sp. nov., a budding bacterium with variable bacteriochlorophyll a production from hypersaline Ekho Lake

Eight Gram-negative, aerobic, pointed and budding bacteria were isolated from various depths of the hypersaline, heliothermal and meromictic Ekho Lake (Vestfold Hills, East Antarctica). The cells contained storage granules and daughter cells could be motile. Bacteriochlorophyll a was sometimes produced, but production was repressed by constant dim light. The strains tolerated a wide range of temperature, pH, concentrations of artificial seawater and NaCl, but had an absolute requirement for sodium ions. Glutamate was metabolized with and without an additional source of combined nitrogen. The dominant fatty acid was C18:1; other characteristic fatty acids were C18:2, C12:0 2-OH, C12:1 3-OH, C16:1, C16:0 and C18:0. The main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine. The DNA G+C base composition was 62-64 mol%. 16S rRNA gene sequence comparisons showed that the isolates were phylogenetically close to the genera Antarctobacter, 'Marinosulfonomonas', Octadecabacter, Sagittula, Sulfitobacter and Roseobacter. Morphological, physiological and genotypic differences to these previously described and distinct genera support the description of a new genus and a new species, Roseovarius tolerans gen. nov., sp. nov. The type strain is EL-172T (= DSM 11457T).

Structures of the psychrophilic Alteromonas haloplanctis alpha-amylase give insights into cold adaptation at a molecular level

BACKGROUND

. Enzymes from psychrophilic (cold-adapted) microorganisms operate at temperatures close to 0 degreesC, where the activity of their mesophilic and thermophilic counterparts is drastically reduced. It has generally been assumed that thermophily is associated with rigid proteins, whereas psychrophilic enzymes have a tendency to be more flexible.

RESULTS

. Insights into the cold adaptation of proteins are gained on the basis of a psychrophilic protein's molecular structure. To this end, we have determined the structure of the recombinant form of a psychrophilic alpha-amylase from Alteromonas haloplanctis at 2.4 A resolution. We have compared this with the structure of the wild-type enzyme, recently solved at 2.0 A resolution, and with available structures of their mesophilic counterparts. These comparative studies have enabled us to identify possible determinants of cold adaptation.

CONCLUSIONS

. We propose that an increased resilience of the molecular surface and a less rigid protein core, with less interdomain interactions, are determining factors of the conformational flexibility that allows efficient enzyme catalysis in cold environments.

Methylopila capsulata gen. nov., sp. nov., a novel non-pigmented aerobic facultatively methylotrophic bacterium

A new genus, Methylopila, and one new species are described for a group of seven strains of facultatively methylotrophic bacteria with the serine pathway of C1 assimilation. These bacteria are aerobic, Gram-negative, non-spore--forming, motile, colourless rods that multiply by binary fission. Their DNA base content ranges from 66 to 70 mol % G + C. Their cellular fatty acid profile consists primarily of C18:1 omega 7 cis-vaccenic and C19:0 cyclopropane acids. The major hydroxy acid is 3-OH C14:0. The main ubiquinone is Q-10. The dominant cellular phospholipids are phosphatidylethanolamine and phosphatidylcholine. The new isolates have a low level of DNA-DNA homology (5-10%) with the type strains of the serine pathway methylobacteria belonging to the genera Methylobacterium, Aminobacter, Hyphomicrobium and Methylorhabdus. Another approach, involving 16S rRNA gene sequence analysis of strain IM1T, has shown that the new isolates represent a separate branch within the alpha-2 subclass of the Proteobacteria. The type species of the new genus is Methylopila capsulata sp. nov., with the type strain IM1T (= VKM B-1606T).

Antarctobacter heliothermus gen. nov., sp. nov., a budding bacterium from hypersaline and heliothermal Ekho Lake

Four Gram-negative, aerobic, pointed and budding bacteria were isolated from various depths of the hypersaline, heliothermal and meromictic Ekho Lake (Vestfold Hills, East Antarctica). The cells contained storage granules and formed rosettes. Daughter cells may be motile. Growth required sodium ions. Nitrate was reduced to nitrite, and dissimilatory reduction of nitrite was possible. DNase and gelatinase were produced. Glutamate was metabolized with and without an additional source of combined nitrogen. The most abundant fatty acid was C18:1; other fatty acids present in lower concentrations were C12:1 3-OH, C16:1, C16:0, C18:0 and C19:0 cyc. The main polar lipids were phosphatidylglycerol and phosphatidylcholine. The DNA base composition was 62.3-62.8 mol% G + C. 16S rDNA sequence comparisons showed the isolates to be phylogenetically related to the genera Sagittula and Roseobacter. Morphological, physiological and genotypic differences to these and distinct characteristics supported the description of a new genus and a new species, Antarctobacter heliothermus gen. nov., sp. nov. The type strain is EL-219T (= DSM 11445T).

Development of a genetic transformation system for an alga-lysing bacterium

Four marine bacteria, Alteromonas sp. strains A27, A28, A29, and A30, that lyse the diatom Skeletonema costatum NIES-324 were isolated from coastal seawater samples. They were also able to lyse the diatoms Thalassiosira sp. and Eucampia zodiacs and the raphidophycean flagellate Chattonella antiqua. Cryptic indigenous plasmids, designated pAS28 and pAS29, were detected in Alteromonas sp. strains A28 and A29, respectively. These plasmids appeared to be similar based on size and restriction site analysis. A shuttle vector that replicates in Escherichia coli and Alteromonas sp. strain A28 was constructed by fusing pAS28 and E. coli vector pCRIIc. The 16-kbp chimeric plasmid, designated pASS1, had the ability to transform strain A28 at a frequency of 10(6) transformants per microg of DNA. Deletion analysis of pASS1 showed that the 4.7-kb EcoRI-HindIII region of pAS28 was essential for plasmid maintenance in strain A28. This EcoRI-HindIII fragment contained an open reading frame which appeared to encode a 708-amino-acid protein.

Acquired thermotolerance and temperature-induced protein accumulation in the extremely thermophilic bacterium Rhodothermus obamensis

Temperature-induced changes in thermotolerance and protein composition were examined in heat-shocked cells and high-temperature-grown cells of the extremely thermophilic bacterium Rhodothermus obamensis. The survival at temperatures superoptimal for growth (90 and 95 degrees C) was enhanced in both heat-shocked cells and high-temperature-grown cells relative to that of cells grown at optimal temperatures. In a comparison of protein composition using two-dimensional gel electrophoresis, putative heat shock proteins (HSPs) and high-temperature growth-specific proteins (HGPs) were detected. N-terminal amino acid sequence analysis revealed that the putative HSPs were quite similar to the ATP-binding subunits of ABC transporters and the HGPs were proteins corresponding to domains II and III of elongation factor Tu. These results suggested that this extreme thermophile has developed temperature-induced responses that include increased survival under hyperthermal conditions, changes in protein composition, and also the production of novel HSPs.

Extremely thermostable phosphoenolpyruvate carboxylase from an extreme thermophile, Rhodothermus obamensis

Phosphoenolpyruvate carboxylase (PEPC) was purified from an extremely thermophilic bacterium, Rhodothermus obamensis, growing optimally at 80 degrees C, which had recently been isolated from a shallow marine hydrothermal vent in Japan. The native enzyme was a homotetramer of 400 kDa in molecular mass, as estimated by gel filtration chromatography, and the subunit exhibited an apparent molecular mass of 100 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum temperature for enzyme activity was 75 degrees C. The enzyme exhibited an absolute requirement for divalent cations and a pH optimum of 8.0. The enzyme was extremely thermostable and there was no loss of enzyme activity on incubation for 2 h at 85 degrees C. The enzyme exhibited a positive allosteric property with acetyl-CoA and fructose 1,6-bisphosphate, and a negative one with L-aspartate and L-malate. These effectors affected not only the thermophilicity but also the thermostability of the enzyme, and the substrate, co-factors, and salts increased the thermostability as well. The extrinsic thermostabilization might be a possible mechanism for adaptation of the enzyme to high temperature.

Enzymes from cold-adapted microorganisms. The class C beta-lactamase from the antarctic psychrophile Psychrobacter immobilis A5

A heat-labile beta-lactamase has been purified from culture supernatants of Psychrobacter immobilis A5 grown at 4 degrees C and the corresponding chromosomal ampC gene has been cloned and sequenced. All structural and kinetic properties clearly relate this enzyme to class C beta-lactamases. The kinetic parameters of P. immobilis beta-lactamase for the hydrolysis of some beta-lactam antibiotics are in the same range as the values recorded for the highly specialized cephalosporinases from pathogenic mesophilic bacteria. By contrast, the enzyme displays a low apparent optimum temperature of activity and a reduced thermal stability. Structural factors responsible for the latter property were analysed from the three-dimensional structure built by homology modelling. The deletion of proline residues in loops, the low number of arginine-mediated H-bonds and aromatic-aromatic interactions, the lower global hydrophobicity and the improved solvent interactions through additional surface acidic residues appear to be the main determinants of the enzyme flexibility.

Metal selectivity of in situ microcolonies in biofilms of the Elbe river

The ultrastructure of natural complex biofilm communities of the Elbe river grown in situ on microscopic glass coverslips was studied by using transmission electron microscopy and energy-dispersive x-ray (EDX) analysis. Characteristic microcolonies which measured between 3.3 and 9.3 microm in diameter were frequently observed. They had an outer envelope and harbored 6 to 30 cells. The cells formed short rods measuring 1.09 +/- 0.28 microm (n = 10) in length and 0.55 + 0.07 microm (n = 21) in width. They were surrounded by a thick layer of electron-transparent, nonosmicated matter, 120 to 300 nm thick. Individual cells exhibited a unique ultrastructural trait, namely, a concentric membrane stack which completely surrounded the cytoplasm. It consisted of three membrane doublets, which showed an overall thickness of 57 to 66 nm. The center-to-center spacing between two membrane doublets was 22.2 +/- 1.0 nm (n = 12). The bacterial cell wall seemed to be of the gram-negative type. The fact that upon shrinkage hexagonal clefts appeared proved the cells to be tightly packed, and septum formation by binary fissions was observed. All of these morphological details indicate that the cells within these microcolonies were actively growing and did not represent spore-like states. EDX analysis showed that only the electron-dense surface deposit of the microcolonies contained Mn and Fe in significant amounts, while these two elements were absent from the intercellular space and the cytoplasm of the microorganisms. In contrast, aluminum ions were able to penetrate the outer envelope of the microcolonies and were detected in the intercellular space. They were, however, completely absent from the microbial cytoplasm, indicating a filter cascade with respect to aluminum. From the ultrastructural data together with the deposition of iron and manganese on the microcolony surface, it appears that these organisms may belong to the genus Siderocapsa or Nitrosomonas. They do not precisely match any of the described species and may therefore represent a new species.

Osmoadaptation by rhizosphere bacteria

The osmolality of rhizosphere soil water is expected to be elevated in relation to bulk-soil water osmolality as a result of the exclusion of solutes by plant roots during water uptake, the release of plant root exudates, and the production of exopolymers by plant roots and rhizobacteria. In contrast, the osmolality of water within highly hydrated bulk soil is low (less than 50 Osm/kg); thus the ability to adapt to elevated osmolality is likely to be important for successful rhizosphere colonization by rhizobacteria. The present review focuses on the osmoadaptive responses of three gram-negative rhizobacterial genera: Rhizobium, Azospirillum, and Pseudomonas. Specifically, we examine the compatible solutes and osmoprotectants utilized by various species within these genera. The adaptation of rhizobacteria to hypoosmotic environments is also examined in the present review. In particular, we focus on the biosynthesis and accumulation of periplasmic glucans by rhizobacteria. Finally, the relationship between rhizobacterial osmoadaptation and selected plant-microbe interactions is considered.

Comamonas testosteroni colony phenotype influences exopolysaccharide production and coaggregation with yeast cells

A Comamonas testosteroni strain was isolated from activated sludge on the basis of its ability to coaggregate with yeast cells. On agar plates the following two types of colonies were formed: colonies with a mucoid appearance and colonies with a nonmucoid appearance. On plates this strain alternated between the two forms, making sectored colonies. In liquid medium with constant agitation no such change was observed. In the absence of agitation and in contact with a glass surface a culture with predominantly nonmucoid-colony-forming cells very rapidly shifted to a culture dominated by mucoid-colony-forming cells. In liquid medium the reverse was observed under stress conditions imposed by hydrogen peroxide, sodium dodecyl sulfate, or starvation. Nonmucoid cells formed very rapidly settling flocs with yeast cells, while coaggregation of mucoid cells with yeast cells did not occur. These findings may be relevant to the behavior of activated sludge microbial communities.

The genus Sphingomonas: physiology and ecology

Exploitation of the metabolic capabilities of the genus Sphingomonas could provide important commercial benefits to biotechnology. Recent advances have demonstrated that these organisms have unique abilities to degrade refractory contaminants, to serve as bacterial antagonists to phytopathogenic fungi, and to secrete the highly useful gellan exopolysaccharides. Unfortunately, Sphingomonas are also animal pathogens and can readily degrade the copper pipes in drinking water distribution systems. The closely related Zymomonas could be important for commercial ethanol production. These Gram-negative aerobic bacteria are characterized by an outer membrane that contains glycosphingolipids, but lacks lipopolysaccharide. Their distribution in environmental samples has not been systematically examined as yet.

Taxonomic study of bacteria isolated from plants: proposal of Sphingomonas rosa sp. nov., Sphingomonas pruni sp. nov., Sphingomonas asaccharolytica sp. nov., and Sphingomonas mali sp. nov

The taxonomic positions of 10 strains of 3-ketolactose-forming bacteria which were isolated from the roots of plants (Rosa sp., Psychotria nairobiensis, Ardisia crispa, Prunus persica, and apple trees) were investigated. The DNA base compositions of these strains ranged from 64.0 to 65.7 mol%, the isoprenoid quinone of each strain was ubiquinone 10, 3-hydroxy fatty acids were lacking in the cellular fatty acids of these organisms, and all of the strains contained a sphingolipid with the long-chain base dihydrosphingosin. These are characteristics of the genus Sphingomonas. On the basis of morphological, physiological, and chemotaxonomic characteristics, together with DNA-DNA hybridization and 16S ribosomal DNA sequence comparison data, we propose the following four new species of the genus Sphingomonas: Sphingomonas rosa (type strain, IFO 15208) for the strains isolated from rose plants and formerly named [Agrobacterium rhizogenes]; Sphingomonas pruni (type strain, IFO 15498) for the strains isolated from Prunus persica; and Sphingomonas asaccharolytica (type strain, IFO 15499) and Sphingomonas mali (type strain, IFO 15500) for the strains isolated from apple trees. Two strains which were isolated from Psychotria nairobiensis and formerly named [Chromobacterium lividum] were identified as Sphingomonas yanoikuyae strains.

Roseobacter algicola sp. nov., a new marine bacterium isolated from the phycosphere of the toxin-producing dinoflagellate Prorocentrum lima

We describe a new species on the basis of phenotypic characteristics and the results of an analysis of small-subunit rRNA sequences. Three strains of this organism were isolated from a culture of the toxin-producing dinoflagellate Prorocentrum lima. These bacteria are gram-negative, strictly aerobic, ovoid organisms that are motile by means of one or two subpolar flagella. They grow at temperatures ranging from 10 to 37 degrees C and in the presence of NaCl concentrations ranging from 0.1 to 2 M and have an absolute requirement for sodium ions. They are strictly aerobic with a nonfermentative type of metabolism and are not able to grow anaerobically in presence or absence of nitrate. They do not denitrify. They exhibit oxidase, catalase, gelatinase, esculinase, beta-galactosidase, and (to a lesser extent) amylase activities. The three strains which we examined require thiamine and biotin for growth. They grow only when glucose, trehalose, saccharose, fructose, maltose, pyruvate, malate, citrate, esculin, 2-ketoglutarate, 5-ketogluconate, glutamate, or shikimate is present as a sole carbon source. The three strains have identical small-subunit rRNA sequences. A phylogenetic analysis of these sequences revealed that these bacteria belong to the alpha subdivision of the Proteobacteria and that they form a distinct and robust monophyletic group with Roseobacter denitrificans and Roseobacter litoralis. This result and the general phenotypic characteristics of the organisms place them in the genus Roseobacter, although they do not produce bacteriochlorophyll a, in contrast to previously described Roseobacter species.(ABSTRACT TRUNCATED AT 250 WORDS)

The elimination of Salmonella typhimurium in coastal waters with various levels of microbiologically hygienic contamination

The biotic elimination of Salmonella typhimurium in coastal sea water is primarily caused by protozoa. The elimination is usually faster in summer than in winter and in the vicinity of waste water outlets partially faster than in coastal areas with less contamination. When the rate of elimination is measured twice in succession in the same sample (primary/secondary culture) the second reduction is considerably faster. This activation is attributed to the multiplication of protozoa (predator-prey-effect). The activation is also possible through E. coli in concentrations such as those found in waste from sewage treatment plants or by Salmonella typhimurium themselves and vice versa. After 12 hours incubation the number of E. coli in the primary culture was still about 58% of the original quantity and 12 hours after a renewed inoculation in the secondary culture only 1%. When salmonella were added to the primary culture it was already impossible to detect E. coli after 12 hours in the secondary culture. Salmonella showed comparable tendencies, although the elimination of salmonella was clearly slower than the elimination of E. coli even after activation with salmonella. In the primary culture E. coli is already recultivatable in a smaller quantity than salmonella. Furthermore the addition of Cycloheximide to the secondary culture provides a considerably better protection for salmonella than for E. coli, so that it can be assumed that other or additional factors are involved in the elimination of E. coli.

Expression of the symbiotic plasmid from Rhizobium leguminosarum biovar trifolii in Sphingobacterium multivorum

An inoculant strain of Rhizobium leguminosarum biovar trifolii containing a Tn5 marked symbiotic plasmid transferred this plasmid by conjugation to Sphingobacterium multivorum, an organism that can be found in soil. The transconjugant bacteria nodulated the roots of white clover (Trifolium repens) seedlings but did not fix atmospheric nitrogen. Microscopic examination revealed abnormal nodule structures. Bacteria isolated from the nodules were shown to be closely related to the recipient S. multivorum and Southern blots of genomic digests probed with nodA DNA confirmed that the transconjugants contained symbiotic genes. This is the first report of the spontaneous transfer, by conjugation, of a symbiotic plasmid from R. leguminosarum biovar trifolii to S. multivorum.

Analysis of competition in soil among 2,4-dichlorophenoxyacetic acid-degrading bacteria

Competition among indigenous and inoculated 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacteria was studied in a native Kansas prairie soil following 2,4-D additions. The soil was inoculated with four different 2,4-D-degrading strains at densities of 10(3) cells per g of soil; the organisms used were Pseudomonas cepacia DBO1(pJP4) and three Michigan soil isolates, strain 745, Sphingomonas paucimobilis 1443, and Pseudomonas pickettii 712. Following 2,4-D additions, total soil DNA was extracted and analyzed on Southern blots by using a tfdA gene probe which detected three of the strains and another probe that detected the fourth strain, S. paucimobilis 1443, which belongs to a different class of 2,4-D degraders. P. cepacia DBO1(pJP4), a constructed strain, outcompeted the other added strains and the indigenous 2,4-D-degrading populations. The S. paucimobilis population was the secondary dominant population, and strain 745 and P. pickettii were not detected. Relative fitness coefficients determined in axenic broth cultures predicted the outcome of competition in soil for some but not all strains. Lag time was shown to be a principal determinant of competitiveness among the strains, but the lag times were significantly reduced in mixed broth cultures, which changed the competitive outcome. Plasmids containing the genes for the 2,4-D pathway were important determinants of competitiveness since plasmid pKA4 in P. cepacia DBO1 resulted in the slower growth characteristic of its original host, P. pickettii, rather than the rapid growth observed when this strain harbors pJP4.

Marinobacter hydrocarbonoclasticus gen. nov., sp. nov., a new, extremely halotolerant, hydrocarbon-degrading marine bacterium

On the basis of phenotypical characteristics and analysis of 16S rRNA sequence, a new species belonging to a new genus is described, and the name Marinobacter hydrocarbonoclasticus is proposed. This organism, isolated from Mediterranean seawater near a petroleum refinery, is a gram-negative, aerobic, rod-shaped bacterium. It grows at NaCl concentrations of 0.08 to 3.5 M and uses various hydrocarbons as the sole source of carbon and energy. Its DNA has a guanine-plus-cytosine content of 52.7 mol%. The 16S rRNA analysis shows a clear affiliation between M. hydrocarbonoclasticus and the gamma group of the phylum Proteobacteria. A close phylogenetic relationship appears among the species Marinomonas vaga, Oceanospirillum linum, Halomonas elongata, and Pseudomonas aeruginosa. Because of the impossibility of finding a single most closely related species, we suggest that this bacterium be assigned to a new genus, at least temporarily. The possibility of a revision of this status when new data appear is, however, not excluded. The type strain is M. hydrocarbonoclasticus SP.17 (= ATCC 49840).

Linear growth and poly(beta-hydroxybutyrate) synthesis in response to pulse-wise addition of the growth-limiting substrate to steady-state heterotrophic continuous cultures of Aquaspirillum autotrophicum

Heterotrophic pyruvate-limited steady-state continuous cultures of the bacterium Aquaspirillum autotrophicum were perturbed with a pulse injection of a small volume of concentrated pyruvate solution. These cultures exhibited an instantaneous change in the growth dynamics, turning from steady state to apparently linear growth. These transient growth-responses had no lag phase and were clearly distinct from unlimited exponential growth according to the initial rates of increase of biomass and substrate disappearance kinetics. A linear accumulation with time of poly(beta-hydroxybutyrate) was observed within the cells. Slopes of these linear responses were negatively correlated with the dilution rate. Physiological bases of linear growth are discussed in the light of the models of H. E. Kubitschek. Poly(beta-hydroxybutyrate) synthesis in the absence of exogenous limitation may serve to protect the cells against a transient metabolic overflow.

Chemical and cultural characterization of CDC group WO-1, a weakly oxidative gram-negative group of organisms isolated from clinical sources

Ninety-six strains of weakly oxidative gram-negative rods isolated primarily from clinical specimens form a distinct group that has been designated Centers for Disease Control (CDC) group WO-1 (WO stands for weak oxidizer). The phenotypic characteristics of CDC group WO-1 were most similar to those of Comamonas acidovorans, Pseudomonas mallei, and CDC pink coccoid group III. The WO-1 group can be differentiated from C. acidovorans by the oxidation of glucose (often weak and sometimes delayed), motility by means of one or two polar flagella, and, when positive, the complete reduction of nitrate and nitrite. Motility and usually the failure to produce arginine dihydrolase distinguish this group from P. mallei. The WO-1 strains differ from the pink coccoid group III by the absence of pink growth pigment, the lack of predominantly coccoid cellular morphology, and usually the inability to produce acid from xylose. The cellular fatty acid compositions of 29 group WO-1 strains were characterized by large amounts of C16:0 and C16:1w7c; smaller amounts of C18:1w7c, C14:0, C12:0, and 3-OH-C10:0; and trace to small amounts of C15:1w6 and C17:0 acids. The fatty acid profile of WO-1, compared with the profiles of other bacteria we have tested previously, was most similar to the profiles of two phenotypically different organisms, Comamonas terrigena (a nonoxidative, multipolar gram-negative rod) and Chromobacterium violaceum (a fermentative gram-negative rod). Ubiquinone-8 was the major quinone in the five WO-1 strains examined. Eighty-five percent of the WO-1 strains were isolated from human specimens. Thirty-three percent were from blood, and 10% were from cerebrospinal fluid.

Temperature inhibition of siderophore production in Azospirillum brasilense

The effect of growth at 42 degrees C on the different components of the siderophore-mediated iron transport that are induced by iron limitation in Azospirillum brasilense was examined. Biosynthesis of the siderophore spirilobactin was strongly inhibited (20-fold) by growth at 42 degrees C, whereas the transport of iron by the ferric-spirilobactin transport system and the induction of the iron-regulated outer membrane proteins were unaffected.

Elongation factor Tu of the extreme thermophilic hydrogen oxidizing bacterium Calderobacterium hydrogenophilum

Protein synthesis elongation factor Tu has been purified from an extreme thermophilic hydrogen oxidizing bacterium Calderobacterium hydrogenophilum. The molecular mass of EF-Tu. GDP is 51,000. The factor is heat stable and loses only 50% of its activity after heating for 5 min at 80 degrees C. Under mild conditions trypsin cleaved EF-Tu. GDP to four main fragments. Only one fragment of Mr = 20,000 had a mobility similar to the trypsin fragment "B" of Escherichia coli EF-Tu. Other peptide fragments of E. coli and C. hydrogenophilum EF-Tu differed in size, but native preparations of both factors are immunologically similar.

Selective bowel decontamination to decrease gram-negative aerobic bacterial and Candida colonization and prevent infection after orthotopic liver transplantation

Gram-negative bacterial and fungal infections are a major cause of morbidity and mortality following liver transplantation. We therefore used selective bowel decontamination (SBD) to eliminate the endogenous source of gram-negative aerobic bacteria and Candida pathogens in an attempt to reduce the high incidence of infection related to these organisms. Thirty consecutive patients undergoing liver transplantation were treated with SBD starting 3 days prior to donor search and continuing for 21 days postliver transplantation. Selective bowel decontamination consisted of administering nonabsorbable antibiotics (Polymixin E, gentamicin, Nystatin) and a low bacterial diet. Surveillance cultures of the throat and rectum were obtained to monitor efficacy of selective bowel decontamination. In addition, in the posttransplant period, tracheal, wound, blood, and bile cultures were obtained to screen for gram-negative bacterial and Candida colonization and infection. Our baseline surveillance culture revealed that 29/30 (97%) of recipients were colonized with gram-negative aerobic bacteria and 16/30 (53%) with Candida. Three days after selective bowel decontamination was started, 26/30 (87%) were free of gram-negative bacteria, and 100% were free of Candida colonization of the gastrointestinal tract. There was a similar reduction in the oropharyngeal gram-negative aerobic bacteria and Candida colonization. In the first 30 days following liver transplantation, gram-negative infections were not diagnosed in any of our patients. Following discontinuation of SBD, recolonization of the gastrointestinal tract with gram-negative aerobic bacteria and Candida occurred within 5 days in 26/28 (90%) and 11/28 (35%), respectively. Our study suggests that prophylactive administration of nonabsorbable antibiotics will markedly reduce gram-negative aerobic bacterial and Candida colonization and appears to reduce the high incidence of infection related to these organisms in the early posttransplant period.

Influence of amino acids on nitrogen fixation ability and growth of Azospirillum spp

The utilization of amino acids for growth and their effects on nitrogen fixation differ greatly among the several strains of each species of Azospirillum spp. that were examined. A. brasiliense grew poorly or not at all on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources. Nitrogen fixation by most A. brasiliense strains was inhibited only slightly even by 10 mM concentrations of these amino acids. In contrast, A. lipoferum and A. amazonense grew very well on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources; nitrogen fixation, which was measured in the presence of malate or sucrose, was severely inhibited by these amino acids. It was concluded that growth on histidine as the sole source of nitrogen, carbon, and energy may be used for the taxonomic characterization of Azospirillum spp. and for the selective isolation of A. lipoferum. The different utilization of various amino acids by Azospirillum spp. may be important for their establishment in the rhizosphere and for their associative nitrogen fixation with plants. The physiological basis for the different utilization of glutamate by Azospirillum spp. was investigated further. A. brasiliense and A. lipoferum exhibited a high affinity for glutamate uptake (Km values for uptake were 8 and 40 microM, respectively); the Vmax was 6 times higher in A. lipoferum than in A. brasiliense. At high substrate concentrations (10 mM), the nonsaturable component of glutamate uptake was most active in A. lipoferum and A. amazonense.(ABSTRACT TRUNCATED AT 250 WORDS)

[Characteristics of dissociation in cultures of Aspergillus brasilense Sp7]

Peculiarities of dissociation in the cultures of nitrogen-fixating soil microorganism Azospirillum brasilense have been studied. The possible transfer among colony-morphology variants is established. The relations between variants are described by the following scheme: R in equilibrium with SR----S Electrophoretic analysis of plasmid contents in different variants of Azospirillum brasilense supposes the possible participation of plasmid DNA in the dissociation process in this microorganism.

Effect of intestinal flora modulation by oral polymyxin treatment on hemopoietic stem cell kinetics in mice

After oral treatment with polymyxin for only 1 day, fecal aerobic gram-negative bacteria were found completely suppressed in C3H/Law mice. Complete suppression of aerobic gram-negative bacteria was accompanied by a reduction of the fecal endotoxin concentration from 100 to 10 micrograms endotoxin per gram of feces as measured with the Limulus amebocyte lysate assay. Oral administration of polymyxin affected hemopoietic stem cell kinetics at different stages. The kinetic behavior of hemopoietic stem cells was determined as the in vivo sensitivity to the S phase specific cytostatic drug hydroxyurea. The hydroxyurea kill of bone marrow spleen colony-forming cells diminished not significantly (p less than 0.10) from 14 to 4% after 2 days of polymyxin treatment. Already after 1 day of treatment the hydroxyurea kill of bone marrow progenitor cells forming granulocyte-macrophage colonies in vitro decreased from 29 to 7% (p less than 0.05). It took 8 days of treatment before the hydroxyurea kill of splenic granulocyte-macrophage colonies was found reduced from 53 to 14% (p less than 0.001). The decreased susceptibility of hemopoietic stem cells to hydroxyurea during polymyxin treatment appears to argue for a role of intestinal aerobic gram-negative bacteria in the regulation of hemopoiesis, probably mediated by endotoxin.