Halomonas sabkhae sp. nov., a moderately halophilic bacterium isolated from an Algerian sabkha.

A novel moderately halophilic bacterium belonging to the genus Halomonas was isolated from brine samples collected from Ezzemoul sabkha in north-eastern Algeria. The cells of strain 5-3(T) were Gram-negative, rod-shaped and non-motile. The strain was catalase- and oxidase-positive and produced an exopolysaccharide. Growth occurred at NaCl concentrations of 5-25% (optimum at 7.5%), at 30-50 degrees C (optimum at 37-40 degrees C) and at pH 6.0-9.0 (optimum at pH 7.5). The major fatty acids were C(12:0) 3-OH, C(16:1)omega7c/iso-C(15:0) 2-OH, C(16:0), C(18:1)omega7c and C(19:0)omega8c cyclo. The G+C content of the genomic DNA was 57.0 mol% (T(m)). The affiliation of strain 5-3(T) with the genus Halomonas was confirmed by 16S rRNA gene sequence comparisons. The most closely related species was Halomonas halmophila, which showed a 16S rRNA gene sequence similarity of 99.7%. However, the level of DNA-DNA relatedness between the novel isolate and the related Halomonas species was less than 31.4%. On the basis of the data from this polyphasic study, strain 5-3(T) represents a novel species of the genus Halomonas, for which the name Halomonas sabkhae sp. nov. is proposed. The type strain is 5-3(T) (=CECT 7246(T)=DSM 19122(T)=LMG 24084(T)).

Establishment of Eubacterium cellulosolvens in the digestive tract of axenic and meroxenic mice: influence of feed cellulose content.

The cellulolytic bacterial species present in the caecum and colon contents of conventionally reared mature mice did not become established in the digestive tract when inoculated to axenic mice, whatever the size of the inoculum or the cellulose content of the diet. The cellulolytic bacterium Eubacterium cellulosolvens SC 10 isolated from mouse digestive flora was unable to become established in the digestive tract of axenic mice whatever the cellulose content of the diet; it requires a feed rich in cellulose and a highly diversified microflora.

Establishment of cellulolytic bacteria in the digestive tract of conventionally reared young mice: effect of the dietary cellulose content in the adult.

Cellulolytic bacteria became established 12 days after birth in the caecum and colon of conventionally-reared mice fed a diet containing 5 p. 100 crude cellulose (Weende). Their population reached a level between 10(6) and 10(7) bacteria per gram of digestive contents in 25-day-old animals. However, variations between animals were very large; 20 to 50% of the individuals were free of cellulolytic bacteria. A low cellulolytic population was observed in adult mice fed a cellulose-free diet. The amount of cellulose in the diet and its nature (crude or pure cellulose) affected the number of cellulolytic bacteria: the higher the percentage of cellulose in the diet, the higher the number of cellulolytic bacteria, in particular with crude cellulose-containing diet.