Arthrobacter mobilis sp. nov., a novel actinobacterium isolated from Cholistan desert soil.

A Gram-stain-positive, aerobic, catalase-positive, oxidase-negative, non-mycelium-forming, motile, rod-shaped with one polar flagellum actinobacterium, designated E918T, was isolated from a desert soil collected in Cholistan desert, Pakistan. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain E918T belonged to the genus Arthrobacter and was most closely related to Arthrobacter deserti CGMCC 1.15091T (97.2 % similarity). The peptidoglycan was of the A3α type and the whole-cell sugar profile was found to contain galactose. The major menaquinone was MK-9(H2). The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two unidentified glycolipids. The major fatty acids identified were anteiso-C15 : 0 and anteiso-C17 : 0. The G+C content of the genomic DNA was 68.69 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between strain E918T and A. deserti CGMCC 1.15091T were 28.0 and 83.4%, respectively. On the basis of its phylogenetic, phenotypic and chemotaxonomic features, strain E918T was considered to represent a novel species of the genus Arthrobacter, for which the name Arthrobacter mobilis sp. nov. is proposed. The type strain of Arthrobacter mobilis is E918T (=JCM 33392T=CGMCC 1.16978T).

Auraticoccus cholistanensis sp. nov., an actinomycete isolated from soil of the Cholistan Desert, and emended description of the genus Auraticoccus.

A Gram-stain-positive, aerobic, non-motile and non-spore-forming actinobacterium, designated as F435T, was isolated from soil sample collected from the Cholistan Desert, Pakistan. The taxonomic position of the strain was established by using a polyphasic taxonomic approach. The cells were coccoid-shaped and found in single or arrangement of pairs. The novel strain grew at 15‒37 °C (optimum, 25‒30 °C), pH 7‒11 (optimum, pH 7-8) and in the presence of 0‒8% (w/v) NaCl (optimum, 0 %). Results of blast analysis based on 16S rRNA gene sequences showed that Auraticoccus monumenti MON 2.2T was its closest relative with 97.4 % similarity followed by Desertihabitans aurantiacus CPCC 204711T (95.2 %). In phylogenetic trees, strain F435T formed a robust cluster with the only member of the genus Auraticoccus. The peptidoglycan isomer present in the cell wall was ll-diaminopimelic acid. The major fatty acid was determined to be anteiso-C15 : 0. Characteristic polar lipids of the strain were diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipids and glycolipids. The predominant menaquinone was MK-9(H4). The genomic G+C content was calculated as 73.5 mol%. The digital DNA-DNA hybridization (GGDC) and average nucleotide identity (ANI) values between strain F435T and A. monumenti MON 2.2T were 24.6 and 81.8 %, respectively. Based on the results of phenotypic, chemotaxonomic, phylogenetic and phylogenomic analyses, strain F435T represents a novel specie of the genus Auraticoccus, for which the name Auraticoccus cholistanensis sp. nov. is proposed. The type strain is F435T (=JCM 33648T=CGMCC 1.17443T). The description of the genus Auraticoccus has also been emended.

PCR-based Screening Approach: A Rapid Method to Detect the Biosynthetic Potential of Antimicrobials in Actinobacterial Strains.

This study aimed to investigate the PCR-based screening strategy for the prediction of the antimicrobial biosynthetic potential of the selected Streptomyces strains originated from an extreme environment (Cholistan Desert, Pakistan). The biosynthetic potential was determined by using both molecular and culture-dependent screening approaches. The four biosynthetic genes clusters, including the pks-1, nrps, cyp P450 hydroxylase (cyps), and glycopeptide oxy b genes, were investigated in the selected strains by PCR amplification, sequencing, and by subsequent bioinformatics approaches. Among the 40 selected Streptomyces strains, 33 strains possessed the nrps gene, 17 strains carried the pks-1 gene, four strains were found to have the cyps gene, and none of the strain carried oxy b gene. The Streptomyces strains including NR-1, NR-10, NR-14, and NR-15 were investigated for in vitro antifungal activity against Fusarium oxysporum, Rhizoctonia solani, and Aspergillus sp. The extracts were analyzed for chemical profiling (TLC and HPLC-UV), and a unique pattern of secondary metabolites was observed. The selected strains exhibited pronounced antifungal activity against the fungal test strains with the zone of inhibition up to 17, 18, and 19 mm, respectively. The study depicts that gene-based screening can be successfully applied to identify potentially bioactive strains by usin a single screening process. This PCR-based approach is rapid and can be used for sorting out and selecting the potential candidate among actinobacterial culture collections. Such a preselection or strain prioritization consequently decreases the time and efforts required for selecting the potential bioactive strain, which then can be subjected to the detailed chemical analysis.This study aimed to investigate the PCR-based screening strategy for the prediction of the antimicrobial biosynthetic potential of the selected Streptomyces strains originated from an extreme environment (Cholistan Desert, Pakistan). The biosynthetic potential was determined by using both molecular and culture-dependent screening approaches. The four biosynthetic genes clusters, including the pks-1, nrps, cyp P450 hydroxylase (cyps), and glycopeptide oxy b genes, were investigated in the selected strains by PCR amplification, sequencing, and by subsequent bioinformatics approaches. Among the 40 selected Streptomyces strains, 33 strains possessed the nrps gene, 17 strains carried the pks-1 gene, four strains were found to have the cyps gene, and none of the strain carried oxy b gene. The Streptomyces strains including NR-1, NR-10, NR-14, and NR-15 were investigated for in vitro antifungal activity against Fusarium oxysporum, Rhizoctonia solani, and Aspergillus sp. The extracts were analyzed for chemical profiling (TLC and HPLC-UV), and a unique pattern of secondary metabolites was observed. The selected strains exhibited pronounced antifungal activity against the fungal test strains with the zone of inhibition up to 17, 18, and 19 mm, respectively. The study depicts that gene-based screening can be successfully applied to identify potentially bioactive strains by usin a single screening process. This PCR-based approach is rapid and can be used for sorting out and selecting the potential candidate among actinobacterial culture collections. Such a preselection or strain prioritization consequently decreases the time and efforts required for selecting the potential bioactive strain, which then can be subjected to the detailed chemical analysis.

Motilibacter deserti sp. nov. and Motilibacter aurantiacus sp. nov., two novel actinobacteria isolated from soil of Cholistan Desert and emended description of the genus Motilibacter.

Two novel actinobacterial strains, designated as E257T and K478T, were isolated from hyper-arid soil samples collected in Cholistan Desert, Pakistan. Comparative analysis of 16S rRNA genes showed that strains E257T and K478T were assigned to the genus Motilibacter, being their closest relative M. rhizosphaerae RS-16T with 97.3% and 96.7% similarities, respectively. The sequence similarity between strain E257T and K478T was 98.9%. Phylogenetic analysis based on 16S rRNA gene sequences and phylogenomic analysis based on multiple genes of conserved core proteins exhibited that these two strains belonged to the genus Motilibacter and formed a robust cluster separated from the two type species of the genus Motilibacter. Average Nucleotide Identity (ANI), Average Amino acid Identity (AAI), digital DNA-DNA hybridization (dDDH) values and Percentage of Conserved Proteins (POCP) calculated from the complete genome sequences indicated strains E257T and K478T were assigned into genus Motilibacter but clearly separated from each other and from the other species of the genus Motilibacter with values below the thresholds for species delineation. The two isolates were found to have chemotaxonomic, cultural and morphological properties consistent with their classification in the genus Motilibacter and also confirmed the differentiation from their closest species. The obtained results demonstrated that strains E257T and K478T represent two novel species of the genus Motilibacter, for which the names Motilibacter desertisp. nov. (type strain E257T = JCM 33651T = CGMCC 1.17159T) and Motilibacter aurantiacus sp. nov. (type strain K478T =JCM 33652T =CGMCC 1.17229T) are proposed.