The taxonomic relationship of certain environmental flavobacteria to the genus Weeksella

Forty environmental strains and reference cultures of Flavobacterium, Cytophaga and Weeksella spp. were examined by numerical taxonomy. Twenty-seven strains were recovered in four phena. Phena 1A and IB comprised 48% of the strains and were sufficiently similar to the genus Weeksella as to suggest possible inclusion in this genus. They could not be accommodated in the existing species W. virosa and W. zoohelcum. Strains from phenon 2 appear to belong neither in the Flavobacterium or the Weeksella genus. Although no reference strains were included in phena 3 and 4 they appear phenotypically to be most similar to F. breve and F. odoratum respectively.     

The taxonomic relationship of certain environmental flavobacteria to the genus Weeksella

Forty environmental strains and reference cultures of Flavobacterium, Cytophaga and Weeksella spp. were examined by numerical taxonomy. Twenty-seven strains were recovered in four phena. Phena 1A and 1B comprised 48% of the strains and were sufficiently similar to the genus Weeksella as to suggest possible inclusion in this genus. They could not be accommodated in the existing species W. virosa and W. zoohelcum. Strains from phenon 2 appear to belong neither in the Flavobacterium or the Weeksella genus. Although no reference strains were included in phena 3 and 4 they appear phenotypically to be most similar to F. breve and F. odoratum respectively.     

Metabolism of 2,6-dimethylnaphthalene by flavobacteria.

Flavobacteria that were able to grow on 2,6-dimethylnaphthalene (2,6-DMN) were isolated from soil. Most were able to oxidize a broad range of aromatic hydrocarbons after growth on 2,6-DMN at rates comparable to that of the oxidation of 2,6-DMN itself. One small group was neither able to grow on naphthalene nor able to oxidize this compound after growth on 2,6-DMN, but metabolized 2,6-DMN by a pathway which converged with that previously described for naphthalene metabolism in pseudomonads. These organisms could also grow on salicylate or methylsalicylate, and in so doing, early enzymes for 2,6-DMN metabolism were induced.     

Ancestral niche separation and evolutionary rate differentiation between sister marine flavobacteria lineages

Marine flavobacteria are specialists for polysaccharide degradation. They dominate in habitats enriched with polysaccharides, but are also prevalent in pelagic environments where polysaccharides are less available. These niches are likely occupied by distinct lineages, but evolutionary processes underlying their niche differentiation remain elusive. Here, genomic analyses and physiological assays indicate that the sister flavobacteria lineages Leeuwenhoekiella and Nonlabens likely explore polysaccharide-rich macroalgae and polysaccharide-poor pelagic niches respectively. Phylogenomic analyses inferred that the niche separation likely occurred anciently and coincided with increased sequence evolutionary rate in Nonlabens compared with Leeuwenhoekiella. Further analyses ruled out the known mechanisms likely driving evolutionary rate acceleration, including reduced selection efficiency, decreased generation time and increased mutation rate. In particular, the mutation rates were determined using an unbiased experimental method, which measures the present-day populations and may not reflect ancestral populations. These data collectively lead to a new hypothesis that an ancestral and transient mutation rate increase resulted in evolutionary rate increase in Nonlabens. This hypothesis was supported by inferring that gains and losses of genes involved in SOS response, a mechanism known to drive transiently increased mutation rate, coincided with evolutionary rate acceleration. Our analyses highlight the evolutionary mechanisms underlying niche differentiation of flavobacteria lineages.     

Deoxyribonucleic acid reassociation in the classification of flavobacteria.

DNA-DNA reassociation studies showed that Flavobacterium emningosepticum strains had a genetic relatedness of 91 to 100% with inter-strain duplexes having high thermal stabilities. The only exception, strain NCTC10016, had an average relatedness of only 43% to other strains of F. meningosepticum. The apparent divergence in DNA base sequence of this strain was reflected in the structural differences of some enzymes. There was a gradation of DNA relatedness among the Flavobacterium group II-b strains, but three strains were sufficiently related to constitute a species. Low levels of genetic relatedness were confirmed between F. meningosepticum and strains of Flavobacterium group II-b, group II-f, F. aquatile, F. breve, F. heparinum, F. pectinovorum, F. odoratum and Moraxella saccharolytica. All strains had base compositions in the range 32 to 46% guanine plus cytosine. The genome sizes of representative strains of F. meningosepticum and Flavobacterium group II-b were 2-50 X 10(9) to 3-52 X 10(9) daltons. The taxonomic implications of these findings are discussed.     

Pigments of some flavobacteria,xanthomonads and corynebacteria

Summary A study of the spectral properties of intracellular pigments in clarified cellular suspensions of 11 flavobacteria, 9 xanthomonads and 2 corynebacteria showed that the flavobacteria are most heterogeneous in their absorption maxima (390, 400–410, 420–424, 476–478 mμ). The corynebacteria absorbed strongly at 400–404 mμ, indicating some similarity to the flavobacteria. The xanthomonads generally absorbed strongly at 404–406 mμ. In these genera, the general absorption properties removed from the procedure the anticipated taxonomic application, although after establishing other features, such study might be of profit especially in the case of designation ofXanthomonas. Supported by Grant E-706, National Institutes of Health, U.S.A. Contribution number 44 of the Institute of Cellular Biology, Univ. of Conn.     

NAD- and NADP-dependent 7alpha-hydroxysteroid dehydrogenases from bacteroides fragilis.

Twenty strains of Bacteroides fragilis were screened for hydroxysteroid oxidoreductase activity in cell-free preparations. Eighteen strains were shown to contain NAD-dependent 7alpha-hydroxysteroid dehydrogenase. Sixteen of the strains containing the NAD-dependent enzyme also contained NADP-depedent 7alpha-hydroxysteroid dehydrogenase, but invariably in lesser amounts. A strain particulary rich in both 7alpha-hydroxysteroid dehydrogenase activities was selected for further study. Measurement of activity as a function of pH revealed a fairly sharp optimal activity range of 9.5--10.0 for the NAD-dependent enzyme and a broad flat optimal range of 7.0--9.0 for the NADP-dependent enzyme. Michaelis constants for trihydroxy-bile acids for the NAD-dependent enzyme were in the range of 0.32--0.34 mM, whereas dihydroxy-bile acids gave a Km of 0.1 mM. Thin-layer chromatography studies on the oxidation product of 3alpha, 7alpha-dihydroxy-5beta-cholanoic acid (chenodeoxycholic acid) by the dehydrogenase revealed a band corresponding to that of synthetic 3alpha-hydroxy, 7-keto-5beta-cholanoic acid. Similarly the oxidation product of chenodeoxycholic acid by both 7alpha-hydroxysteroid dehydrogenase and commercially available 3alpha-hy-droxysteroid dehydrogenase revealed a band corresponding to that of synthetic 3,7-diketo-5beta-cholanoic acid. Neither of these two oxidation products could be distinguished from those by the Escherichia coli dehydrogenase oxidation previously reported. Disc-gel electrophoresis of a cell-free lyophilized preparation indicated one active band for NAD-dependent activity of mobility similar to that for the NADP-dependent E. coli enzyme. The NADP-dependent dehydrogenase was unstable and rapidly lost activity after polyacylamide disc-gel electrophoresis, ultracentrifugation, freezing on refrigeration at 4 degrees C. No 3 alpha- or 12alpha-oriented oxidoreductase activity was demonstrated in any of the strains examined.     

Metronidazole in prevention and treatment of bacteroides infections after appendicectomy.

The frequency of non-clostridial anaerobic infection was studied in 95 patients who had undergone acute appendicectomy: 49 received prophylactic metronidazole and 46 received placebo. Anaerobic infection did not develop in any of the metronidazole-treated patients, but infections did develop in nine (19%) of the 46 controls. Metronidazole is conveniently administered by suppository to patients who cannot take oral drugs. Five patients with intra-abdominal infections caused by non-clostridial anaerobes were successfully treated with metronidazole.     

A note on starch hydrolysis and beta-glucuronidase activity among flavobacteria

Most flavobacteria tested with the fluorogenic substrate 4-methylumbelliferyl-beta-D-glucuronide possessed beta-glucuronidase (GUD), but when some of the same strains were tested with the API ZYM gallery, all were negative for GUD. Conflicting reports also appear in the literature about starch hydrolysis among flavobacteria. We observed that the results obtained can depend on the medium used and the length of incubation. Our results indicate that GUD activity and starch hydrolysis are more widely distributed in the genus Flavobacterium than previously reported.     

Metronidazole in prevention and treatment of bacteroides infections in elective colonic surgery.

A double-blind randomised trial was carried out among 46 patients undergoing elective colonic surgery; 27 patients received prophylactic metronidazole and 19 received placebo. Anaerobic infections did not develop in any of the metronidazole-treated patients, but did develop in 11 (58%) of 19 controls who were subsequently successfully treated with metronidazole.     

Deoxyribonucleic acid methylation and development in Caulobacter bacteroides

The stalked bacterium Caulobacter bacteroides, which displays a series of developmental changes during its life cycle, was shown to contain the methylated deoxyribonucleic acid (DNA) nucleotide bases N(6)-methyladenine and 5-methylcytosine as well as the enzymes required for the synthesis of these bases. A difference in the specific activity of these enzymes was observed between swarmer cells, which are low in activity, and stalked cells, which are high in activity. This difference was not reflected in the methylation patterns in the DNA of the two cell types since C. bacteroides DNA is essentially completely methylated with respect to C. bacteroides methylases.     

The relationship between legal abortion and marriage.

A study using the abortion-birth ratios for residents of each U.S. state for the second half of 1970 and for all of 1971 was done to determine if legal abortions reduced marriages. Data showed that trends were consistent with the hypothesis that a relationship exists between l egalized abortion-birth ratios and trends in crude marriage rates among states between 1967 and 1971 with reduction in crude marriage rates in the states with the relatively high abortion-birth ratios. Change in po licy on induced abortions may be responsible for the increased trend in the U.S. crude marriage rate from 1959-1970 and for its levelling off in 1971 and 1972. Analysis of data also suggested that there is a relation ship between less restrictive abortion policies and a decline in crude marriage rates. An estimation of the number of marriages postponed for at least one year following legal abortion indicated that about 1 abortion in 10 delays a marriage when all the decline in marriage rates were caused by increased abortions and when no legal abortions were subs titutes for illegal abortions. Results were obtained employing general measures for variables, but stronger relationships might be produced if more refined measures which consider race, age, parity, and marital status were introduced.