Botryobacter ruber gen. nov., sp. nov., a novel member of the family Hymenobacteraceae

Microbulbifer spongiae sp. nov., isolated from marine sponge Diacarnus erythraeanus

A novel bacterium, designated as MI-GT, was isolated from marine sponge Diacarnus erythraeanus. Cells of strain MI-GT are Gram-stain-negative, aerobic, and rod or coccoid-ovoid in shape. MI-GT is able to grow at 10-40 °C (optimum, 28 °C), with 1.0-8.0% (w/v) NaCl (optimum, 4.0%), and at pH 5.5-9.0 (optimum, pH 8.0). The 16S rRNA gene sequence of strain MI-GT shows 98.35, 97.32 and 97.25% similarity to those of Microbulbifer variabilis Ni-2088T, Microbulbifer maritimus TF-17T and Microbulbifer echini AM134T, respectively. Phylogenetic analysis also exhibits that strain MI-GT falls within a clade comprising members of the genus Microbulbifer (class Gammaproteobacteria). The genome size of strain MI-GT is 4478124 bp with a G+C content of 54.51 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain MI-GT and other type strains are 71.61-76.44% (ANIb), 83.27-84.36% (ANIm) and 13.4-18.7% (dDDH), respectively. These values are significantly lower than the recommended threshold values for bacterial species delineation. Percentage of conserved proteins and average amino acid identity values among the genomes of strain MI-GT and other closely related species are 52.04-59.13% and 67.47-77.21%, respectively. The major cellular fatty acids of MI-GT are composed of summed feature 8 (C18 : 1 ω7c or C18 : 1 ω6c), iso-C11 : 0 3-OH, iso-C15 : 0, C16 : 0, and summed feature 9 (C17 : 1 iso ω9c or C16 : 0 10-methyl). The polar lipids of MI-GT mainly consist of phosphatidylethanolamine, phosphatidylglycerol, aminolipid, and two glycolipids. The major respiratory quinone is Q-8. Based on differential phenotypic and phylogenetic data, strain MI-GT is considered to represent a novel species of genus Microbulbifer, for which the name Microbulbifer spongiae sp. nov. is proposed. The type strain is MI-GT (=MCCC 1K07826T=KCTC 8081T).

Sabulibacter ruber gen. nov., sp. nov., a novel bacterium in the family Hymenobacteraceae, isolated from desert soil

A novel Gram-stain-negative, aerobic, oxidase-positive, catalase-positive, non-motile, short rod-shaped, red-pigmented strain, designated as SYSU D00434T, was isolated from a dry sandy soil sample collected from the Gurbantunggut desert in Xinjiang, north-west PR China. Strain SYSU D00434T was found to grow at 4–37 °C (optimum, 28–30 °C), pH 6.0–8.0 (optimum, pH 7.0) and with 0–1.5 % (w/v) NaCl (optimum, 0–0.5 %). The predominant respiratory quinone was MK-7 and the major fatty acids (>10 %) were C16 : 1  ω5c, iso-C15 : 0, summed feature 3 (C16 : 1  ω6c and/or C16 : 1  ω7c) and summed feature 4 (anteiso-C17 : 1 B and/or iso-C17 : 1 I). The polar lipids consisted of phosphatidylethanolamine, two unidentified polar lipids, two unidentified aminolipids, two unidentified phospholipids and two unidentified glycolipids. The genomic DNA G+C content of strain SYSU D00434T was 50.6 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SYSU D00434T belonged to the family Hymenobacteraceae , and shared a sequence similarity of less than 94.6 % to all validly named taxa. Based on the phenotypic, phylogenetic and chemotaxonomic properties, strain D00434T is proposed to represent a new species of a new genus, named Sabulibacter ruber gen. nov., sp. nov., within the family Hymenobacteraceae . The type strain is SYSU D00434T (=CGMCC 1.18624T=KCTC 82276T=MCCC 1K04975T).

From ecophysiology to cultivation methodology: filling the knowledge gap between uncultured and cultured microbes

Earth is dominated by a myriad of microbial communities, but the majority fails to grow under in situ laboratory conditions. The basic cause of unculturability is that bacteria dominantly occur as biofilms in natural environments. Earlier improvements in the culture techniques are mostly done by optimizing media components. However, with technological advancement particularly in the field of genome sequencing and cell imagining techniques, new tools have become available to understand the ecophysiology of microbial communities. Hence, it becomes easier to mimic environmental conditions in the culture plate. Other methods include co-culturing, emendation of growth factors, and cultivation after physical cell sorting. Most recently, techniques have been proposed for bacterial cultivation by employing genomic data to understand either microbial interactions (network-directed targeted bacterial isolation) or ecosystem engineering (reverse genomics). Hopefully, these techniques may be applied to almost all environmental samples, and help fill the gaps between the cultured and uncultured microbial communities.