A taxonomic study was performed on strain YIM 31775T, which was isolated from a soil sample collected from Yunnan Province, China. The isolate was chemo-organotrophic, aerobic and Gram-negative. Cells were short rods and motile, with one or more polar flagella. Growth temperature and pH ranged from 4 to 55 °C and 6·5 to 12·0, respectively; the optimum growth temperature and pH were 28–37 °C and 7·0–9·0, respectively. Q-8 was the predominant respiratory lipoquinone. The major fatty acids were C16 : 1 ω7c (42·4 %) and C16 : 0 (28·1 %). The DNA G+C content was 62·4±0·3 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain YIM 31775T should be placed within the family ‘Oxalobacteraceae’, in which it formed a distinct lineage. Based on the high 16S rRNA gene sequence divergence and phenotypic characteristics, it is proposed that strain YIM 31775T should be classified as representing a novel member of the family ‘Oxalobacteraceae’, for which the name Naxibacter alkalitolerans gen. nov., sp. nov. is proposed. The type strain is YIM 31775T (=CCTCC AA 204003T=KCTC 12194T).

A Gram-positive, motile, short-rod-shaped strain, designated YIM 004T, was isolated from a forest-soil sample collected from Lijiang, Yunnan Province, China, and was investigated using a polyphasic taxonomic approach. The isolate contained chemotaxonomic markers that corresponded to those of its phylogenetic neighbour, Georgenia muralis, i.e. it possessed peptidoglycan type A4α with lysine as the diagnostic cell-wall diamino acid, the predominant menaquinone was MK-8(H4) and the major fatty acid was ai-C15 : 0. The G+C content of the genomic DNA was 72.9 mol%. Strain YIM 004T exhibited a 16S rRNA gene sequence similarity of 97.3 % and a DNA–DNA relatedness value of 18 % with respect to G. muralis DSM 14418T. On the basis of the phenotypic and genotypic differences between the isolate and G. muralis, strain YIM 004T represents a novel species of the genus Georgenia, for which the name Georgenia ruanii sp. nov. is proposed. The type strain is YIM 004T (=CCTCC AB 204065T=DSM 17458T=KCTC 19029T). In addition, an emended description of the genus Georgenia is presented.

The giant panda evolved from omnivorous bears. It lives on a bamboo-dominated diet at present, but it still retains a typical carnivorous digestive system and is genetically deficient in cellulose-digesting enzymes. To find out whether this endangered mammalian species, like other herbivores, has successfully developed a gut microbiota adapted to its fiber-rich diet, we conducted a 16S rRNA gene-based large-scale structural profiling of the giant panda fecal microbiota. Forty-five captive individuals were sampled in spring, summer, and late autumn within 1 year. Significant intraindividual variations in the diversity and structure of gut microbiota across seasons were observed in this population, which were even greater than the variations between individuals. Compared with published data sets involving 124 gut microbiota profiles from 54 mammalian species, these giant pandas, together with 9 captive and 7 wild individuals investigated previously, showed extremely low gut microbiota diversity and an overall structure that diverged from those of nonpanda herbivores but converged with those of carnivorous and omnivorous bears. The giant panda did not harbor putative cellulose-degrading phylotypes such as Ruminococcaceae and Bacteroides bacteria that are typically enriched in other herbivores, but instead, its microbiota was dominated by Escherichia/Shigella and Streptococcus bacteria. Members of the class Clostridia were common and abundant in the giant panda gut microbiota, but most of the members present were absent in other herbivores and were not phylogenetically related with known cellulolytic lineages. Therefore, the giant panda appears not to have evolved a gut microbiota compatible with its newly adopted diet, which may adversely influence the coevolutionary fitness of this herbivore. IMPORTANCEThe giant panda, an endangered mammalian species endemic to western China, is well known for its unique bamboo diet. Unlike other herbivores that have successfully evolved anatomically specialized digestive systems to efficiently deconstruct fibrous plant matter, the giant panda still retains a gastrointestinal tract typical of carnivores. We characterized the fecal bacterial communities from a giant panda population to determine whether this animal relies on its symbiotic gut microbiota to cope with the complex carbohydrates that dominate its diet, as is common in other herbivores. We found that the giant panda gut microbiota is low in diversity and highly variable across seasons. It also shows an overall composition typical of bears and entirely differentiated from other herbivores, with low levels of putative cellulose-digesting bacteria. The gut microbiota of this herbivore, therefore, may not have well adapted to its highly fibrous diet, suggesting a potential link with its poor digestive efficiency.

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