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Thirteen strains of a new acetogenic bacterium were isolated from the rumen contents of lambs, llamas and bisons. This paper is the first report of Gram-positive coccoid spore-forming bacteria occurring in chains and able to use H2 + CO2 as energy source and produce acetate from this gas mixture. One of them, chosen as the reference strain for its efficiency in utilizing H2/CO2 likely via the acetyl-CoA pathway, was characterized in detail. The G + C ratio of the DNA of the organism was 46.5 mol%. The temperature and pH optimum were 37 degrees-40 degrees C and 6.3-6.8, respectively. Numerous organic substrates including some o-methylate aromatic compounds were used heterotrophically. The full 16S rRNA gene sequence was determined. The phylogeny, physiology, morphology and numerous features described here are sufficiently different from those of any bacteria described today to justify the definition of a new species. The name "New acetogenic bacterium" is temporarily proposed, awaiting a future taxonomic revision of the genus Clostridium.

Un test enzymatique simple, rapide et peu couteux a ete utilise pour detecter la presence d'une glycerol-deshydrogenase de type II (induite par le glycerol et l'hydroxyacetone) ou de type IV (induite seulement par l'hydroxyacetone) chez 1.000 souches appartenant a Escherichia coli et Shigella. Une glycerol-deshydrogenase de type II a ete trouvee chez 97 % des souches de E. coli testees. Cette activite n'a ete detectee chez aucune espece de Shigella a l'exception de S. flexneri serotype 6 biotype Manchester. Une glycerol-deshydrogenase de type IV a ete trouvee chez S. dysenteriae serotype 1, S. flexneri serotype 6 biotypes Boyd 88, Manchester «variant» et Herfordshire, et S. boydii serotypes 7, 11, 13, 14 et 15. Les autres serotypes de Shigella ne presentent aucune de ces deux activites enzymatiques.

The anaerobic glycerol pathway was studied in seven enterobacterial species selected as representative of different behaviours in terms of anaerobic glycerol dissimilation. The presence of oxidative and reductive pathways of the dha regulon in Klebsiella pneumoniae enabled the cells to grow fermentatively on glycerol. The first two enzymes of the dha regulon (glycerol dehydrogenase type I and dihydroxyacetone kinase) represent the oxidative branch, while the latter two (glycerol dehydratase and 1,3-propanediol dehydrogenase) represent the reductive branch of glycerol fermentation. The slower utilization of glycerol by K. oxytoca was attributed to low production of 1,3-propanediol. K. oxytoca lacked glycerol dehydratase and demonstrated low 1,3-propanediol dehydrogenase activity. K. planticola and K. ozaenae differed from K. pneumoniae and K. oxytoca in lacking the ability to grow on glycerol. K. planticola lacked both enzymes of the reductive branch of glycerol fermentation, and K. ozaenae possessed glycerol dehydrogenase only. K. rhinoscleromatis and Hafnia alvei, like Escherichia coli, did not possess a dha regulon. The glycerol dehydrogenase type II of H. alvei was distinct from that of E. coli. The phenotypic diversity of anaerobic glycerol dissimilation may have taxonomic applications.

A number of methods have been proposed to assess the viability of cells without culture. Each method is based on criteria that reflect different levels of cellular integrity or functionality. As a consequence, the interpretation of viability is often ambiguous. The purposes of this work were to evaluate the capacity of current viability markers to distinguish between live and dead Escherichia coli K-12 cells. Methods that assess ‘viability’ by the demonstration of metabolic activities (esterase activity, active electron transport chain, transport of glucose), cellular integrity (membrane integrity, presence of nucleic acids) or the building up of cellular material (cell elongation) have been evaluated in live and UV- or heat-killed cells. With live cells, viability markers detected cells in counts similar to the colony count. However, these so-called viability markers could stain dead cells for some time after the lethal treatment. For the UV-killed cells, residual activities were detected even after 48 h of storage at 20 °C. However, for heat-treated cells, these activities disappeared within hours after heat treatment. Only a combination of fluorescence in situ hybridization with rRNA probes and cell elongation in response to nutrients (in the presence of an inhibitor of cell division) had the ability to differentiate live from dead cells. Problems in the definition of a viable but nonculturable state are in part due to the lack of a clear definition of bacterial death. We consider death as an irreversible state where no growth, cell elongation or protein synthesis may occur.

Pasteurella multicida was examined for glucose and mannose transport. P. multocida was shown to possess a phosphoenolpyruvate (PEP):mannose phosphotransferase system (PTS) that transports glucose as well as mannose and was functionally similar to the Escherichia coli mannose PTS. Phosphorylated proteins with molecular masses similar to those of E. coli mannose PTS proteins were visualized when incubated with 32 P-PEP. The presence of an enzyme IIA Glc which could play an important role in regulation, as described in other Gram-negative bacteria, was detected. The enzymes of the pentose-phosphate pathway were present in P. multocida grown on glucose. The activity of 6-phosphofructokinase (the key enzyme of the Embden-Meyerhof pathway (EMP)), was very low in cell extracts, suggesting that EMP is not the major pathway for glucose catabolism.

A study of D-glucose oxidation by Acinetobacter species was carried out. Glucose-oxidizing strains were found distributed among almost all Acinetobacter species. 14C-glucose oxidation kinetics by non-proliferating cells with separation of oxidation products (14C-gluconate) by DEAE-cellulose paper chromatography was studied. Inhibition of glucose dehydrogenase (GDH) activity by 11 carbohydrates (mono- and disaccharides) and determination of the kinetic parameters showed that glucose oxidation was due to the action of membrane-bound GDH (inactive in vivo on disaccharides). On the basis of GDH inhibition patterns obtained, two groups were individualized. The first group of strains (identified as A. calcoaceticus, A. baumannii, A. lwoffii, A. johnsonii and Acinetobacter species 3, 9, 10 and 11) showed a greater affinity for glucose than the second group (A. haemolyticus, A. junii and Acinetobacter species 6 and 12). Restoration of GDH activity after addition of pyrroloquinoline quinone (PQQ) was studied in 187 strains previously found unable to oxidize glucose. GDH activity of 150 out of 166 strains identified as A. baumannii, A. johnsonii, A. lwoffii and Acinetobacter species 11 and 12 was restored. Eighteen of 21 strains identified as A. haemolyticus and Acinetobacter species 6 were unable to produce acid from glucose after addition of PQQ. Our results confirm that the former taxonomic scheme for the genus Acinetobacter (2 species differing only by glucose oxidation) is untenable and that, accordingly, identification of Acinetobacter strains at the species level must be performed using more modern methods, i.e. carbon source utilization tests.