Microbial carbon fixation and its influencing factors in saline lake water.

Microbial carbon fixation in saline lakes constitutes an important part of the global lacustrine carbon budget. However, the microbial inorganic carbon uptake rates in saline lake water and its influencing factors are still not fully understood. Here, we studied in situ microbial carbon uptake rates under light-dependent and dark conditions in the saline water of Qinghai Lake using a carbon isotopic labeling (14C-bicarbonate) technique, followed by geochemical and microbial analyses. The results showed that the light-dependent inorganic carbon uptake rates were 135.17-293.02 µg C L-1 h-1 during the summer cruise, while dark inorganic carbon uptake rates ranged from 4.27 to 14.10 µg C L-1 h-1. Photoautotrophic prokaryotes and algae (e.g. Oxyphotobacteria, Chlorophyta, Cryptophyta and Ochrophyta) may be the major contributors to light-dependent carbon fixation processes. Microbial inorganic carbon uptake rates were mainly influenced by the level of nutrients (e.g., ammonium, dissolved inorganic carbon, dissolved organic carbon, total nitrogen), with dissolved inorganic carbon content being predominant. Environmental and microbial factors jointly regulate the total, light-dependent and dark inorganic carbon uptake rates in the studied saline lake water. In summary, microbial light-dependent and dark carbon fixation processes are active and contribute significantly to carbon sequestration in saline lake water. Therefore, more attention should be given to microbial carbon fixation and its response to climate and environmental changes of the lake carbon cycle in the context of climate change.

Culturomics- and metagenomics-based insights into the microbial community and function of rhizosphere soils in Sinai desert farming systems.

BACKGROUND: The microbiome of the Sinai Desert farming system plays an important role in the adaptive strategy of growing crops in a harsh, poly-extreme, desert environment. However, the diversity and function of microbial communities under this unfavorable moisture and nutritional conditions have not yet been investigated. Based on culturomic and metagenomic methods, we analyzed the microbial diversity and function of a total of fourteen rhizosphere soil samples (collected from twelve plants in four farms of the Sinai desert), which may provide a valuable and meaningful guidance for the design of microbial inoculants. RESULTS: The results revealed a wide range of microbial taxa, including a high proportion of novel undescribed lineages. The composition of the rhizosphere microbial communities differed according to the sampling sites, despite similarities or differences in floristics. Whereas, the functional features of rhizosphere microbiomes were significantly similar in different sampling sites, although the microbial communities and the plant hosts themselves were different. Importantly, microorganisms involved in ecosystem functions are different between the sampling sites, for example nitrogen fixation was prevalent in all sample sites while microorganisms responsible for this process were different. CONCLUSION: Here, we provide the first characterization of microbial communities and functions of rhizosphere soil from the Sinai desert farming systems and highlight its unexpectedly high diversity. This study provides evidence that the key microorganisms involved in ecosystem functions are different between sampling sites with different environment conditions, emphasizing the importance of the functional microbiomes of rhizosphere microbial communities. Furthermore, we suggest that microbial inoculants to be used in future agricultural production should select microorganisms that can be involved in plant-microorganism interactions and are already adapted to a similar environmental setting.

Dongia deserti sp. nov., Isolated from the Gurbantunggut Desert Soil.

A Gram-stain-negative, aerobic, short rod-shaped strain, designated as SYSU D60009T, was isolated from a dry sandy soil sample collected from the Gurbantunggut Desert in Xinjiang, northwest China. Strain SYSU D60009T was observed to grow at 15-42 °C (optimum at 37 °C), pH 4.0-10.0 (optimum at 7.0), and with 0-0.5% (w/v) NaCl (optimum, 0%). The strain grew well on R2A agar, and colonies were smooth, white-pigmented, and circular with low convexity. The polar lipids consisted of phosphatidylethanolamine, aminolipid, aminophospholipid, and unknown lipids. The major cellular fatty acid (> 10%) was C16:0 and the predominant respiratory quinone was Q-10. Whole genome sequencing of strain SYSU D60009T revealed 6,132,710 bp with a DNA G + C content of 63.6%. The ANI and dDDH values of strains SYSU D60009T to Dongia mobilis CGMCC 1.7660 T were 72.8% and 19.0%, respectively. Based on the phenotypic, phylogenetic, and chemotaxonomic properties, strain SYSU D60009T represents a novel species of the genus Dongia, for which the name Dongia deserti sp. nov. is proposed, the type strain is SYSU D60009T (= CGMCC 1.16441 T = KCTC 52790 T).

Salinity Impact on Composition and Activity of Nitrate-Reducing Fe(II)-Oxidizing Microorganisms in Saline Lakes.

Nitrate-reducing Fe(II)-oxidizing (NRFeOx) microorganisms contribute to nitrogen, carbon, and iron cycling in freshwater and marine ecosystems. However, NRFeOx microorganisms have not been investigated in hypersaline lakes, and their identity, as well as their activity in response to salinity, is unknown. In this study, we combined cultivation-based most probable number (MPN) counts with Illumina MiSeq sequencing to analyze the abundance and community compositions of NRFeOx microorganisms enriched from five lake sediments with different salinities (ranging from 0.67 g/L to 346 g/L). MPN results showed that the abundance of NRFeOx microorganisms significantly (P < 0.05) decreased with increasing lake salinity, from 7.55 × 103 to 8.09 cells/g dry sediment. The community composition of the NRFeOx enrichment cultures obtained from the MPNs differed distinctly among the five lakes and clustered with lake salinity. Two stable enrichment cultures, named FeN-EHL and FeN-CKL, were obtained from microcosm incubations of sediment from freshwater Lake Erhai and hypersaline Lake Chaka. The culture FeN-EHL was dominated by genus Gallionella (68.4%), while the culture FeN-CKL was dominated by genus Marinobacter (71.2%), with the former growing autotrophically and the latter requiring an additional organic substrate (acetate) and Fe(II) oxidation, caused to a large extent by chemodenitrification [reaction of nitrite with Fe(II)]. Short-range ordered Fe(III) (oxyhydr)oxides were the product of Fe(II) oxidation, and the cells were partially attached to or encrusted by the formed iron minerals in both cultures. In summary, different types of interactions between Fe(II) and nitrate-reducing bacteria may exist in freshwater and hypersaline lakes, i.e., autotrophic NRFeOx and chemodenitrification in freshwater and hypersaline environments, respectively. IMPORTANCE NRFeOx microorganisms are globally distributed in various types of environments and play a vital role in iron transformation and nitrate and heavy metal removal. However, most known NRFeOx microorganisms were isolated from freshwater and marine environments, while their identity and activity under hypersaline conditions remain unknown. Here, we demonstrated that salinity may affect the abundance, identity, and nutrition modes of NRFeOx microorganisms. Autotrophy was only detectable in a freshwater lake but not in the saline lake investigated. We enriched a mixotrophic culture capable of nitrate-reducing Fe(II) oxidation from hypersaline lake sediments. However, Fe(II) oxidation was probably caused by abiotic nitrite reduction (chemodenitrification) rather than by a biologically mediated process. Consequently, our study suggests that in hypersaline environments, Fe(II) oxidation is largely caused by chemodentrification initiated by nitrite formation by chemoheterotrophic bacteria, and additional experiments are needed to demonstrate whether or to what extent Fe(II) is enzymatically oxidized.

Microbial response to multiple-level addition of grass organic matter in lake sediments with different salinity.

Water surface expansion of saline lakes usually causes the inundation of surrounding grassland, leading to the increase of terrestrial grass organic matter (OM) input to the lakes and the decrease of lake salinity. However, the influence of terrestrial grass OM input increase and salinity decrease on organic carbon mineralization and microbial community composition remains unknown in saline lakes. Here, microbial mineralization of terrestrial grass (Achnatherum splendens) OM at different quantity levels in lake sediments with different salinity was investigated by performing microcosm experiments. The results showed that the CO2 production rates increased with the increase of grass OM supply in the studied sediments with different salinity, which may be driven by certain microbial groups (e.g. Bacteroidota, Firmicutes, and Ascomycota). The increase of grass OM supply reduced the richness of prokaryotic community, which will decrease the size and complexity of the studied microbial networks, but increase the interaction between prokaryotic and fungal taxa. Taken together, our results suggest that the increase of terrestrial grass OM input caused by lake expansion would enhance the mineralization of organic carbon and affect the community composition and interactions of related microorganisms in lake sediments with different salinity.

Aquiflexum lacus sp. nov., isolated from a lake sediment sample.

A novel Gram-staining negative, crescent-like or rod-shaped, non-motile bacterium, designated strain CUG 91378 T, was isolated from a sediment sample of Qinghai Lake, Qinghai Province, China. The strain was red-colored, and catalase- and oxidase-positive. Strain CUG 91378 T was able to grow at 15-37 °C (optimum, 28 °C), pH 7-9 (pH 7.0) and in the presence of up to 3.0% (w/v) NaCl (0-2%). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CUG 91378 T formed a well-supported monophyletic clade with Aquiflexum balticum DSM 16537 T (95.4%) and Aquiflexum aquatile Z0201T (93.2%). The DNA G + C content of CUG 91378 T was 39.0%. Low (< 87%) average nucleotide identity (ANI) and (< 26%) digital DNA-DNA hybridization (dDDH) values were observed between strain CUG 91378 T and its closest species on the phylogenetic trees. The sole respiratory quinone of strain CUG 91378 T was MK-7. The predominant fatty acids (> 5.0%) were iso-C15:0 (19.1%), iso-C16:0 (12.0%), iso-C16:1 H (10.9%), iso-C16:0 3OH (9.2%), iso-C17:0 3OH (7.7%), C17:1ω6c (6.1%) and anteiso-C15:0 (5.8%). Strain CUG 91378 T contained as phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and four unidentified lipids (L1, L2, L3 and L4). Based on the data from the current polyphasic study, the isolate represents a novel species of the genus Aquiflexum for which the name Aquiflexum lacus is proposed. The type strain of the proposed new taxon is CUG 91378 T (= KCTC 62637 T = CGMCC 1.13988 T).

Lunatibacter salilacus gen. nov., sp. nov., a member of the family Cyclobacteriaceae, isolated from a saline and alkaline lake sediment.

A non-motile, Gram-staining negative, catalase- and oxidase-positive, crescent-rod shaped bacterium, designated strain CUG 91308T, was isolated from a sediment sample of Qinghai Lake, Qinghai Province, China. Colonies on OSM agar were round, smooth, flat and pinkish-orange in colour. Strain CUG 91308T could grow at 15-37 °C, pH 6-12 and in the presence of up to 7.0 % NaCl (w/v). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CUG 91308T belonged to the family Cyclobacteriaceae and formed a clade with the genus Lunatimonas in the phylogenetic tree, but separated from any species of the known genera within the family. The genomic DNA G+C content is about 42.1 %. The predominant fatty acids (>10 %) were iso-C15 : 0 (21.1 %), summed feature 3 (C16 : 1 ω7c / C16 : 1 ω6c / iso-C15 : 0 2OH) (14.3 %), iso-C17 : 0 3OH (12.3 %) and summed feature 9 (iso-C17 : 1 ω9c / C16 : 0 10-methyl) (10.6 %). The polar lipids of strain CUG 91308T were phosphatidylethanolamine (PE) and four unidentified polar lipids. Strain CUG 91308T contained MK-7 as the major respiratory quinone. On the basis of phenotypic, genotypic and phylogenetic data, strain CUG 91308T represents a novel species of a novel genus in the family Cyclobacteriaceae, for which the name Lunatibacter salilacus gen. nov., sp. nov. is proposed. The type strain of the proposed new isolate is CUG 91308T (=KCTC 62636T=CGMCC 1.13593T).

Distinct co-occurrence patterns of prokaryotic community between the waters and sediments in lakes with different salinity.

Temporal variations and co-occurrence patterns of the prokaryotic community in saline lakes remain elusive. In this study, we investigated the temporal variations of the prokaryotic community in six lakes with different salinity by using Illumina sequencing. The results showed that prokaryotic community compositions exhibited temporal variations in all studied lakes, which may be partially caused by temporal fluctuations of environmental variables (e.g. salinity, temperature, total nitrogen). Salinity fluctuations exhibited stronger influences on temporal variations of prokaryotic community composition in the lakes with low salinity than in those with high salinity. Stochastic factors (i.e. neutral processes) also contributed to temporal variations of prokaryotic community composition, and their contributions decreased with increasing salinity in the studied saline lakes. Network analysis showed that prokaryotic co-occurrence networks of the studied lakes exhibited non-random topology. Salinity affected the phylogenetic composition of nodes in the studied networks. The topological features (e.g. average connectivity and modularity) of the studied networks significantly differed between lake waters and sediments. Collectively, these results expand our knowledge of the mechanisms underlying prokaryotic community assembly and co-occurrence relationships in saline lakes with different salinity.

Vitreimonas flagellata gen. nov., sp. nov., a novel member of the family Hyphomonadaceae isolated from an activated sludge sample.

A coccobacilli-shaped proteobacterium, designated strain SYSU XM001T, was isolated from an activated sludge sample collected from JiMei sewage treatment plant, Xiamen, PR China. Cells were Gram-stain-negative, catalase-positive and oxidase-negative. The 16S rRNA gene sequence of strain SYSU XM001T shared less than 92 % sequence identities with members of the class Alphaproteobacteria, with highest sequence similarity to Aquidulcibacter paucihalophilus TH1-2T (91.6 %; family Hyphomonadaceae, order Rhodobacterales). The strain exhibited growth at 25-37 °C, pH 7.0-9.0 and in the presence of up to 1 % (w/v) NaCl. Its chemotaxonomic features included ubiquinone-10 as the respiratory isoprenologue, iso-C16 : 0, 10-methyl C16 : 0 TSBA and anteiso-C17 : 0 as major cellular fatty acids and monoglycosyldiglyceride, glucuronopyranosyldiglyceride and two unidentified glycolipids as the main polar lipids. The DNA G+C content was determined to be 62.9 % (draft genome). Analyses of the phylogenetic data and differences in the chemotaxonomic and biochemical features from related genera in the family Hyphomonadaceae indicated that strain SYSU XM001T merits representation of a novel species of a novel genus, for which the name Vitreimonas flagellata gen. nov., sp. nov. is proposed. The type strain of Vitreimonas flagellata is SYSU XM001T (=CGMCC 1.16661T=KCTC 62915T).

Microlunatus speluncae sp. nov., a novel actinobacterium isolated from a Karstic subterranean environment sample.

A novel actinobacterial strain, designated SYSU K12189T, was isolated from a soil sample collected from a Karst cave in Xingyi county, Guizhou province, south-western China. The taxonomic position of the strain was investigated using a polyphasic approach. Cells of the strain were observed to be aerobic and Gram-stain positive. On the basis of 16S rRNA gene sequence similarities and phylogenetic analysis, strain SYSU K12189T is closely related to the type strains of the genus Microlunatus, Microlunatus parietis 12-Be-011T (98.5% sequence similarity), Microlunatus nigridraconis CPCC 203993T (98.4%) and Microlunatus cavernae YIM C01117T (96.6%), and is therefore considered to represent a member of the genus Microlunatus. DNA-DNA hybridization values between strain SYSU K12189T and related type strains of the genus Microlunatus were < 70%. In addition, LL-diaminopimelic acid was found to be the diagnostic diamino acid in the cell wall peptidoglycan. The major isoprenoid quinone was identified as MK-9(H4), while the major fatty acids (> 10%) were found to be anteiso-C15:0, iso-C15:0, iso-C16:0 and iso-C14:0. The polar lipids were found to contain diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, three glycolipids and two unidentified lipids. The genomic DNA G+C content of strain SYSU K12189T was determined to be 69.4 mol%. On the basis of phenotypic, genotypic and phylogenetic data, strain SYSU K12189T is concluded to represent a novel species of the genus Microlunatus, for which the name Microlunatus speluncae sp. nov. is proposed. The type strain is SYSU K12189T (= KCTC 39847T = DSM 103947T).

Streptomyces cavernae sp. nov., a novel actinobacterium isolated from a karst cave sediment sample.

A novel actinobacterial strain, designated SYSU K10008T, was isolated from a soil sample collected from a karst cave in Xingyi County, Guizhou Province, south-western PR China. The taxonomic position of the strain was investigated by using a polyphasic approach. Cells of the strain were aerobic, Gram-stain-positive and non-motile. On the basis of 16S rRNA gene sequence similarities and the results of phylogenetic analysis, strain SYSU K10008T was most closely related to Streptomyces cyaneus CGMCC 4.1671T, and shared the highest sequence identity of 98.3 % based on the NCBI database. In addition, ll-diaminopimelic acid was the diagnostic diamino acid in cell-wall peptidoglycan. The whole-cell sugars were glucose and rhamnose. The major isoprenoid quinone was MK-9(H6), while the major fatty acids (>10 %) were C16 : 0, iso-C16 : 0, anteiso-C15 : 0 and summed feature 3 (C16 : 1 ω7c/C16  : 1 ω6c). The polar lipids contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and one unidentified lipid. The genomic DNA G+C content of strain SYSU K10008T was 70.5 mol%. On the basis of phenotypic, genotypic and phylogenetic data, strain SYSU K10008T represents a novel species of the genus Streptomyces, for which the name Streptomyces cavernae sp. nov. is proposed. The type strain is SYSU K10008T (=KCTC 39850T=DSM 104115T).

Aestuariivirga litoralis gen. nov., sp. nov., a proteobacterium isolated from a water sample, and proposal of Aestuariivirgaceae fam. nov.

A Gram-stain-negative, non-motile, short rod and aerobic bacterium, designated strain SYSU M10001T, was isolated from a water sample collected from the coastal region of Pearl River Estuary, Guangdong Province, PR China. Strain SYSU M10001T showed optimal growth at 28 °C, pH 7.0 and in the absence of NaCl. Phylogenetic analyses based on 16S rRNA gene sequences and concatenation of 20 protein markers revealed a distinct lineage for strain SYSU M10001T in the order Rhizobiales. Strain SYSU M10001T showed highest 16S rRNA gene sequence similarities to Hyphomicrobium nitrativorans NL23T (91.1 %) and Hyphomicrobium hollandicum IFAM KB-677T (91.1 %). The respiratory ubiquinone was Q-8. The polar lipids of the strain comprised diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminophospholipid, two unidentified phospholipids and three unidentified lipids. The predominant cellular fatty acids identified were C19 : 0cyclo ω8c, summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0. The G+C content was determined to be 65.5 % (genome). On the basis of differences in the phenotypic, physiological and biochemical characteristics, and results of the phylogenetic analyses, strain SYSU M10001T is proposed to represent a novel species in a novel genus for which the name Aestuariivirga litoralis gen. nov., sp. nov. The type strain of the type species Aestuariivirga litoralis is SYSU M10001T (=NBRC 112960T=KCTC 52945T). Besides, the distinct phylogenetic lineage and the distinct chemotaxonomic profile among the families in the order Rhizobiales indicated that strain SYSU M10001T should represent a new family for which the name Aestuariivirgaceae fam. nov. is proposed.

Pseudofrancisella aestuarii gen. nov., sp. nov., a novel member of the family Francisellaceae isolated from estuarine seawater.

A Gram-negative, aerobic, non-motile and non-spore forming bacterium, designated strain SYSU WZ-2T, was isolated from an estuarine seawater sample. Growth of strain SYSU WZ-2T was observed at temperature range of 10-40° C (optimum, 32 °C), pH range of 6-10 (optimum, pH 7-8) and in the presence of up to 5.0% NaCl (w/v). The DNA G+C content of the novel strain was determined to be 30.1% (genome). The major polar lipids were found to be diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, an unidentified aminolipid, two unidentified aminophospholipids and two unidentified phospholipids. The major fatty acids were C18:0 3-OH (27.5%), C18:1ω9c (19.3%), C16:0 (17.0%) and C14:0 (12.9%). The respiratory quinone was found to be ubiquinone Q8. Pairwise comparison of the 16S rRNA gene sequence showed that strain SYSU WZ-2T shares high identities with members of the genera Francisella (94.8-95.9%) and Allofrancisella (93.8-94.2%). The phylogenetic dendrograms based on 16S rRNA gene sequences with the members of the family Francisellaceae showed that the strain SYSU WZ-2T formed a distinct phylogenetic lineage well separated from the members of the genera Francisella and Allofrancisella. MALDI-TOF mass spectrometric analysis also depicted a different profile for strain SYSU WZ-2T compared with those of members of the genera Francisella and Allofrancisella. Based on the above results and differences in phenotypic and chemotaxonomic features, strain SYSU WZ-2T is characterized to represent a new species of a novel genus, for which the name Pseudofrancisella aestuarii gen. nov., sp. nov. is proposed (type strain SYSU WZ-2T = KCTC 52557T = CGMCC 1.13718T).

Nocardioides speluncae sp. nov., a novel actinobacterium isolated from a karstic subterranean environment sample.

A novel actinobacterial strain, designated YIM ART13T, was isolated from a soil sample collected from a karst cave in Xingyi county, Guizhou province, South western China. The taxonomic position of the strain was investigated using a polyphasic approach. Cells of the strain were found to aerobic and Gram-stain positive. On the basis of 16S rRNA gene sequence analysis, strain YIM ART13T was found to be closely related to Nocardioides pakistanensis NCCP 1340T (96.1% sequence similarity) and is therefore considered to represent a member of the genus Nocardioides. In addition, LL-diaminopimelic acid was identified as the diagnostic diamino acid in the cell wall peptidoglycan. The whole cell sugars were found to be mannose, galactose, glucose and ribose. The major isoprenoid quinone was identified as MK-8(H4), while the major fatty acids (> 10%) were identified as iso-C16:0, C18:1ω9c and C18:0 10-methyl. The polar lipids were found to contain diphosphatidylglycerol, phosphatidylglycerol phosphatidylinositol and phosphatidylinositol mannoside, an unidentified phospholipid. The genomic DNA G+C content of strain YIM ART13T was determined from the draft genome sequence to be 70.1 mol%. On the basis of phenotypic, genotypic and phylogenetic data, strain YIM ART13T represents a novel species of the genus Nocardioides, for which the name Nocardioides speluncae sp. nov. is proposed. The type strain is YIM ART13T (= KCTC 39593T = DSM 100493T).

Flaviflagellibacter deserti gen. nov., sp. nov., a novel member of the order Rhizobiales isolated from a desert soil.

A motile, rod-shaped and yellow coloured proteobacterium, designated strain SYSU D60017T, was isolated from a desert soil sample. The bacterium was found to be an obligately aerobic, mesophilic and neutrophilic chemo-heterotroph. Cells were observed to be Gram-stain negative, catalase positive and oxidase positive. The major cellular fatty acids were identified as C19:0ω8c cyclo and Summed Feature 8 (C18:1ω7c and/or C18:1ω6c). The main respiratory quinone identified was ubiquinone-10. The DNA G + C content was determined to be 63.8% based on draft genome sequence data. The polar lipids detected were identified as diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and five unidentified polar lipids. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SYSU D60017T is a member of the order Rhizobiales, but forms a distinct phylogenetic lineage. The differences in the phenotypic characteristics from members of related genera and its distinct phylogenetic position suggested that the isolate SYSU D60017T represents a novel species of a novel genus within the order Rhizobiales, for which the name Flaviflagellibacter deserti gen. nov., sp. nov. is proposed. The type strain of the new taxon is SYSU D60017T (= CGMCC 1.16444T = NBRC 112958T).

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

Strain SYSU D60016T, a rod-shaped bacterium that tends to form clusters, was isolated from a soil sample collected from the Gurbantunggut desert, China. Cells were Gram-stain-negative, catalase-negative and oxidase-positive. The 16S rRNA gene sequence of strain SYSU D60016T shared less than 94 % sequence identity with members of the family Hymenobacteraceae. The strain exhibited growth at 15-50 °C, pH 6-8 and in the presence of up to 3 % (w/v) NaCl. Its chemotaxonomic features included MK-7 as the respiratory menaquinone, iso-C15 : 0 and summed feature 4 (iso-C17 : 1 I and/or anteiso-C17 : 1 B) as major cellular fatty acids and phosphatidylethanolamine as the main polar lipid. The DNA G+C content was determined to be 50.1 % (genome). Analyses of the phylogenetic data and differences in the chemotaxonomic and biochemical features from related genera in the family Hymenobacteraceae indicated that strain SYSU D60016T merits representation of a novel species of a novel genus in the family Hymenobacteraceae. The name Botryobacter ruber gen. nov., sp. nov. is, therefore, proposed to represent the phylogenetic position of strain SYSU D60016T in the family Hymenobacteraceae. The type strain of the proposed new taxon is SYSU D60016T (=KCTC 52794T=NBRC 112957T).

Nocardia aurea sp. nov., a novel actinobacterium isolated from a karstic subterranean environment.

A novel actinobacterium, designated strain SYSU K10002T, was isolated from a soil sample collected from a karst cave in Xingyi county, Guizhou province, south-western China. The taxonomic position of the strain was investigated using a polyphasic approach. Cells of the strain were aerobic and Gram-stain-positive. On the basis of 16S rRNA gene sequence similarities and phylogenetic analysis, strain SYSU K10002T was most closely related to the type strains of Nocardiaaltamirensis NBRC 108246T (99.0 % sequence similarity) and Nocardiatenerifensis NBRC 101015T (98.8 %) and is therefore considered to represent a member of the genus Nocardia. DNA-DNA hybridization values between strain SYSU K10002T and the closely related type strains of the genus Nocardia were less than 70 %. In addition, meso-diaminopimelic acid was the diagnostic diamino acid in the cell-wall peptidoglycan. The whole-cell sugars were arabinose, ribose and galactose. The major isoprenoid quinone was MK-8(H4,ω-cycl), while the major fatty acids (>10 %) were C16 : 0, C18 : 1ω9c and C18 : 0 10-methyl. The polar lipids contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified glycolipid. Mycolic acids were present. The genomic DNA G+C content of strain SYSU K10002T was 67.4 mol%. On the basis of phenotypic, genotypic and phylogenetic data, strain SYSU K10002T represents a novel species of the genus Nocardia, for which the name Nocardiaaurea sp. nov. is proposed. The type strain is SYSU K10002T (=KCTC 39849T=DSM 103986T).

Microbacterium suaedae sp. nov., isolated from Suaeda aralocaspica.

Two bacterial strains, YZYP 306T and YZGP 509, were isolated from the halophyte Suaeda aralocaspica collected from the southern edge of the Gurbantunggut desert, north-west China. Cells were Gram-stain-positive, aerobic, non-motile, short rods. Strain YZYP 306T grew at 4-40 °C, while strain YZGP 509 grew at 4-42 °C, with optimum growth at 28 °C, and they both grew at pH 6.0-12.0 and 0-15 % (w/v) NaCl. Phylogenetic analyses of the 16S rRNA gene sequences placed the two strains within the genus Microbacterium with the highest similarities to Microbacterium indicum BBH6T (97.8 %) and Microbacterium sorbitolivorans SZDIS-1-1T (97.2 %). The average nucleotide identity value between YZYP 306T and M. indicum BBH6T was 78.3 %. The genomic DNA G+C contents of strains YZYP 306T and YZGP 509 were 68.49 and 68.53 mol%, respectively. The characteristic cell-wall amino acid was ornithine. Whole-cell sugars were galactose, mannose and ribose. The acyl type of the peptidoglycan was glycolyl. The major cellular fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The major menaquinones were MK-10 and MK-11. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, an unidentified phospholipid and an unidentified glycolipid. These results are consistent with the classification of the two strains into the genus Microbacterium. On the basis of the evidence presented in this study, strains YZYP 306T and YZGP 509 are representatives of a novel species in the genus Microbacterium, for which the name Microbacterium suaedae sp. nov. is proposed. The type strain is YZYP 306T (=CGMCC 1.16261T=KCTC 49101T).

Expression and characterisation of a pH and salt tolerant, thermostable and xylose tolerant recombinant GH43 ß-xylosidase from Thermobifida halotolerans YIM 90462T for promoting hemicellulose degradation.

A gene encoding a ß-xylosidase (designated as Thxyl43A) was cloned from strain Thermobifida halotolerans YIM 90462T. The open reading frame of this gene encodes 550 amino acid residues. The gene was over-expressed in Escherichia coli and the recombinant protein was purified. The monomeric Thxyl43A protein presented a molecular mass of 61.5 kDa. When p-nitrophenyl-ß-d-xylopyranoside was used as the substrate, recombinant Thxyl43A exhibited optimal activity at 55 °C and pH 4.0 to 7.0, being thermostable by maintaining 47% of its activity after 30 h incubation at 55 °C. The recombinant enzyme retained more than 80% residual activity after incubation at pH range of 4.0 to 12.0 for 24 h, respectively, which indicated notable thermostability and pH stability of Thxyl43A. Moreover, Thxyl43A displayed high catalytic activity (> 60%) in presence of 5-35% NaCl (w/v) or 1-20% ionic liquid (w/v) or 1-50 mM xylose. These properties suggest that Thxyl43A has potential for promoting hemicellulose degradation and other industrial applications.

Desertimonas flava gen. nov., sp. nov. isolated from a desert soil, and proposal of Ilumatobacteraceae fam. nov.

A non-motile, coccobacilli-shaped and yellow-coloured bacterium, designated strain SYSU D60003T, was isolated from a desert soil sample. Cells were Gram-stain-positive, catalase-negative and oxidase-positive. The whole cell hydrolysates contained ll-diaminopimelic acid as the diagnostic amino acid. The major fatty acids were C16 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and iso-C16 : 0. The respiratory menaquinones were MK-9(H8), MK-9(H4) and MK-9(H6). The DNA G+C content was determined to be 70.2 % (genome). The polar lipids detected were diphosphatidylglycerol, an unidentified glycolipid and seven unidentified polar lipids. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SYSU D60003T belonged to the order Acidimicrobiales (class Acidimicrobiia), but formed a clade closely linked to members of the genus Ilumatobacter. Data from a polyphasic taxonomy study suggested that the isolate represents a novel species of a novel genus in the order Acidimicrobiales, for which the name Desertimonas flava gen. nov., sp. nov. is proposed. The type strain of the proposed new taxon is SYSU D60003T (=KCTC 39917T=NBRC 112924T). Additionally, the new taxon along with the genus Ilumatobater (family unassigned) were distinctly separated from the related families Acidimicrobiaceae, Iamiaceae and 'Microtrichaceae' in the phylogenetic trees, besides presenting a unique 16S rRNA gene signature nucleotides. Therefore, we propose a new family Ilumatobacteraceae fam. nov. within the order Acidimicrobiales to accommodate members of these two genera.