Rhizobium japonicum USDA191 is a member of a new group of Rhizobium japonicum strains found in China. This strain is one of several strains shown to be salt-tolerant and fast-growing; it is unique in being the only strain of this group that effectively nodulates American soybean cultivars. For these reasons strain USDA 191 was chosen for further study and comparison to the common American Rhizobium japonicum isolate USDA 1 10. Strain USDA 19 1 has a doubling time of 3.2 h in complex medium and grows in concentrations of up to 0.4 M-NaCl, while strain USDAl 10, which has a doubling time of 12 h, is severely inhibited in media containing 0.1 MNaCl. Under salt stress conditions, intracellular levels of K+ and glutamate were shown to increase. A comparison based on carbohydrate metabolism, DNA homology and protein patterns on polyacrylamide gels reveals that strain USDA191 is more closely related to the fastgrowing rhizobia than to Rhizobium japonicum. However, the strain retains capacity to nodulate American soybean and cowpea cultivars effectively.
Aims: The purpose of our research is to isolate salt-sensitive mutants and to study the genes involved in salt tolerance of the salt-tolerant bacterium Sinorhizobium meliloti 042BM. Methods: Wild type S. meliloti 042BM bacteria are able to grow at a NaCl concentration of 0.6 mol l )1 . A transposon Tn5-1063a mutagenesis library of S. meliloti 042BM was constructed and eight salt-sensitive mutants were isolated, which were unable to growth on FY plates containing 0.4 mol l )1 NaCl.Significance: Our interest is to provide information about the mechanism of salt tolerance in bacteria by studying the genes involved in salt tolerance. Here, seven different genes were identified. These genes include omp10 encoding a cell outer membrane protein, relA encoding (p)ppGpp synthetase, greA encoding a transcription cleavage factor, nuoL encoding NADH dehydrogenase I chain L transmembrane protein, a putative nuclease/helicase gene and two unknown genes. Based on these findings, we suggest that the regulation of salt tolerance of S. meliloti 042BM is complex and on several levels.
The marine bacterial strain HY9T was isolated from sediment from the South China Sea. Strain HY9T is aerobic, heterotrophic and rose-pigmented. The cells are non-motile and curved, i.e. ring-like or horseshoe-shaped. The 16S rRNA gene sequence of strain HY9T was determined and blast searches revealed that it possessed significant sequence similarities with respect to Cyclobacterium species (92.8–93.6 %). Phylogenetic analysis confirmed that strain HY9T was tightly clustered with members of the genus Cyclobacterium. The cellular morphology and chemotaxonomic and phenotypic properties of strain HY9T showed that it should be classified as a member of the genus Cyclobacterium. Significant evolutionary distances and a range of phenotypic features distinguished strain HY9T from previously described Cyclobacterium species. Hence, strain HY9T represents a novel species in the genus Cyclobacterium, for which the name Cyclobacterium lianum sp. nov. is proposed. The type strain is HY9T (=CGMCC 1.6102T=JCM 14011T). On the basis of this study and previously described properties of Cyclobacterium species, an emended description of the genus Cyclobacterium is proposed.
A novel marine bacterial strain, HY1T, was isolated from sediment of the South China Sea. The strain was aerobic and heterotrophic and formed saffron yellow-pigmented colonies on marine agar 2216. Cells were non-motile, Gram-negative rods, frequently occurring in chains. blastn searches revealed that the 16S rRNA gene sequence of strain HY1T showed high similarity with those of members of the genera Gillisia (91.7–93.8 %) and Salegentibacter (92.6–93.5 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain clustered with members of both Salegentibacter and Gillisia and phylogenetic trees constructed using three different methods (neighbour-joining, maximum-parsimony and minimum-evolution) indicated that strain HY1T clustered more frequently with members of the genus Salegentibacter. The DNA G+C content of strain HY1T was 44.4 mol% and its major cellular fatty acids (⩾5 % of the total fatty acids) were iso-15 : 1 (5.0 %), iso-15 : 0 (6.8 %), anteiso-15 : 0 (6.4 %), 15 : 0 (10.4 %), iso-16 : 0 (13.5 %), summed feature 3 (comprising iso-15 : 0 2-OH and/or 16 : 1ω7c; 6.3 %), iso-17 : 0 3-OH (5.2 %) and 17 : 0 2-OH (5.0 %). Cells contained menaquinone 6. Based on the phylogenetic and phenotypic analyses, strain HY1T should be classified as representing a novel species within the genus Salegentibacter, for which the name Salegentibacter catena sp. nov. is proposed. The type strain is HY1T (=CGMCC 1.6101T=JCM 14015T). Based on this study and on previously described Salegentibacter species, an emended description of the genus Salegentibacter is given.
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