Optimization of ectoine production from Nesterenkonia xinjiangensis and one-step ectoine purification

In the current study, the optimization of ectoine production byNesterenkonia xinjiangensisand purification of ectoine from the bacterial cell extract were performed for the first time. Various carbon sources (glucose, sucrose, maltose, lactose, mannitol, and xylose) and nitrogen sources (ammonium nitrate, ammonium phosphate, ammonium chloride, ammonium oxalate, ammonium sulphate, and ammonium acetate), were used to optimize ectoine production. Subsequently, the effects of salt, pH and, concentrations of carbon and nitrogen source on ectoine production were optimized by response surface methodology (RSM). Ultimately, high pure (over 99%) and yield (98%) of ectoine from bacterial cells extracted was obtained by a single-step process using cation exchange chromatography. This study provides information that higher ectoine production can be achieved from this bacterial isolate by optimizing the factors influencing ectoine production and thus can be used as a new and alternative ectoine producer.

Nesterenkonia sedimenti sp. nov., isolated from marine sediment

A Gram-staining-positive actinobacteria strain, designated MY13^T, was isolated from deep-sea sediment of the western Pacific Ocean and subjected to a taxonomic polyphasic investigation. Based on the results, cells were aerobic, irregular short rod, non-motile and non-spore-forming. Colonies were cream, circular, smooth, convex, opaque and 1.0-2.0 mm in diameter after growth on MZ2 medium at 40 °C for 72 h. Strain MY13^T grew at 4-50 °C (optimum, 40 °C), pH 7-12 (pH 9) and 0.5-15% (w/v) NaCl (3.5%). The 16S rRNA gene sequence analysis revealed that strain MY13^T is affiliated with the genus Nesterenkonia and closely related to Nesterenkonia populi GP10-3^T (96.6%). Digital DNA-DNA hybridization (dDDH) values and average nucleotide identity (ANI) differentiated it from its closest relatives, with values ranging from 19.8% to 22.4% and 72.6% to 78.0%, respectively. Chemotaxonomic analysis showed that the major menaquinone of strain MY13^T was MK-7; major cellular fatty acids were anteiso-C_17:0, anteiso-C_15:0 and iso-C_16:0; whole-cell sugars were galactose and xylose; the peptidoglycan type was L-Lys-Gly-D-Asp; and polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unknown glycolipids, one unknown polar lipid and two unknown lipids. The G+C content of genomic DNA was 63.1 mol%. Based on the physiological, chemotaxonomic and phylogenetic data, strain MY13^T is a novel species of the genus Nesterenkonia, for which the name Nesterenkonia sedimenti sp. nov. is proposed. The type strain is MY13^T (= LMG 28111^T = MCCC 1A09979^T = JCM 19767^T = CGMCC 1.12784^T).

Nesterenkonia ebinurensis sp. nov., a Novel Actinobacterium Isolated From Populus euphratica

During our studies focused on the microorganism diversity and community structure of Populus euphratica at Ebinur lake wetland nature reserve in Xinjiang Uyghur Autonomous Region, PR China, a Gram-positive, aerobic, short rod-shaped bacterium without flagellum, designated as MD2^T, was isolated from a piece of resina on Populus euphratica. The isolate grew at temperature of 10-45 °C (optimum 37 °C), pH of 7.0-12.0 (optimum pH 8.0) and NaCl concentration of 1-18% (optimum 3%, w/v). Based on the 16S rRNA gene sequences and the phylogenetic analysis, the strain shared the highest sequence similarities to Nesterenkonia alkaliphila JCM 19766^T (96.3%), Nesterenkonia populi KCTC 29119^T (95.9%), Nesterenkonia alba CCTCC AB 207011^T (95.5%), and was placed within the radiation of Nesterenkonia species in the phylogenetic trees. The draft genome of the isolate was sequenced, which comprised 3,739,891 bp with G + C content of 63 mol%, and was annotated to contain 3614 protein-coding genes, 44 tRNA genes and 5 rRNA genes. Chemotaxonomic analysis indicated that the main respiratory quinones were MK-8 and MK-9, the predominant cellular fatty acids were anteiso-C_17:0, anteiso-C_15:0 and iso-C_16:0, the major polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol andphosphatidylinositol. According to the phenotypic, chemotaxonomic and phylogenetic features, strain MD2^T is considered to represent a novel species, for which the name Nesterenkonia ebinurensis sp. nov. is proposed. The type strain is MD2^T (= KCTC 52999^T = MCCC 1K03343^T).

Nesterenkonia muleiensis sp. nov., a novel actinobacterium isolated from sap of Populus euphratica

A novel, Gram-stain-positive, aerobic, non-endospore-forming, non-motile and rod-shaped bacterium designated RB2^T was isolated from sap of Populus euphratica collected in Mulei county, Xinjiang province, PR China. RB2^T was able to grow at 10-45 °C (optimum 35 °C), pH 6.0-12.0 (optimum 8.0) and with 0-12 % (w/v) NaCl (optimum 1 %). The genomic DNA G+C content was 63.5 % (from the genome sequence). The results of the chemotaxonomic analysis indicated that the predominant isoprenoid quinones were MK-8 and MK-9. The major fatty acids were anteiso-C_15 : 0 and anteiso-C_17 : 0. The major polar lipids of RB2^T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two glycolipids. The peptidoglycan type of RB2^T was A4α, l-Lys-Gly-l-Glu. The results of the phylogenetic analysis, along with the phenotypic and chemotaxonomic characteristics, indicate that strain RB2^T represents a novel species of the genus Nesterenkonia, for which the name Nesterenkonia muleiensis sp. nov. is proposed. The type strain is RB2^T (=MCCC 1K03528^T=KCTC 49017^T).

Genome-Based Taxonomic Classification of the Phylum Actinobacteria

The application of phylogenetic taxonomic procedures led to improvements in the classification of bacteria assigned to the phylum Actinobacteria but even so there remains a need to further clarify relationships within a taxon that encompasses organisms of agricultural, biotechnological, clinical, and ecological importance. Classification of the morphologically diverse bacteria belonging to this large phylum based on a limited number of features has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees. Here, draft genome sequences of a large collection of actinobacterial type strains were used to infer phylogenetic trees from genome-scale data using principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families, and genera, as well as many species and a few subspecies were shown to be in need of revision leading to proposals for the recognition of 2 orders, 10 families, and 17 genera, as well as the transfer of over 100 species to other genera. In addition, emended descriptions are given for many species mainly involving the addition of data on genome size and DNA G+C content, the former can be considered to be a valuable taxonomic marker in actinobacterial systematics. Many of the incongruities detected when the results of the present study were compared with existing classifications had been recognized from 16S rRNA gene trees though whole-genome phylogenies proved to be much better resolved. The few significant incongruities found between 16S/23S rRNA and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences. Similarly good congruence was found between the discontinuous distribution of phenotypic properties and taxa delineated in the phylogenetic trees though diverse non-monophyletic taxa appeared to be based on the use of plesiomorphic character states as diagnostic features.

Nesterenkonia pannonica sp. nov., a novel alkaliphilic and moderately halophilic actinobacterium

An alkaliphilic and moderately halophilic bacterial strain characterized by optimal growth at pH 9.0-10.0 and with 5-7 % (w/v) NaCl, designated BV-35^T, was isolated from water of a soda pan located in Kiskunság National Park, Hungary. Cells of the orange-pigmented colony were Gram-stain-positive, non-motile and non-endospore-forming coccoid rods. The isolate was strictly aerobic, catalase-positive and oxidase-negative. Strain BV-35^T displayed a peptidoglycan similar to type A4α, l-Lys-l-Glu (A11.54 according to www.peptidoglycan-types.info) but containing additionally 4-aminobutyric acid. Menaquinone-7 (MK-7) was the predominant isoprenoid quinone, and anteiso-C15 : 0 and anteiso-C17 : 0 were its major cellular fatty acids. The DNA G+C content of strain BV-35^T was 65.4 mol%. Based on 16S rRNA gene sequence similarities, the novel isolate showed the closest relationship to Nesterenkonia populi GP 10-3^T (97.9 %). The DNA-DNA relatedness between BV-35^T and N. populi was 46.7 %. The distinguishing phenotypic and genetic results of this polyphasic study revealed that strain BV-35^T represents a novel member of the genus Nesterenkonia, for which the name Nesterenkonia pannonica sp. nov. is proposed. The type strain is BV-35^T (=DSM 29786^T=NCAIM B 02606^T).

Nesterenkonia cremea sp. nov., a bacterium isolated from a soda lake

A Gram-stain-positive, aerobic, non-motile, rod-shaped, non-endospore-forming bacterial strain, 10CT, was isolated from Lonar soda lake in India. Based on the 16S rRNA gene sequence analysis, this strain was identified as belonging to the genus Nesterenkonia and was most closely related to the type strains of Nesterenkonia lacusekhoensis (99.1 %, sequence similarity), Nesterenkonia aethiopica (96.9 %), Nesterenkonia flava (96.9 %) and related of the genus Nesterenkonia (<96.6 %, sequence similarity). However, the DNA-DNA relatedness of strain 10CT with N. lacusekhoensis KCTC 19283T was only 34.6±0.9. The DNA G+C content of strain 10CT was 68.6 mol%. Strain 10CT was an aerobic microbe with optimal growth at 37 °C, pH 7.5-8.0 and 5-6 % (w/v) NaCl. The cell-wall peptidoglycan of strain 10CT was of the type A4α (l-Lys-l-Glu). The major polar lipids present were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylcholine. The major isoprenoid quinones were MK-7, MK-8 and MK-9. Major fatty acids of strain 10CT were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The results of phylogenetic, chemotaxonomic and biochemical tests allowed a clear differentiation of strain 10CT, which represents a novel member of the genus Nesterenkonia for which the name Nesterenkonia cremea sp. nov. is proposed. The type strain is 10CT (=LMG 29100T=KCTC 39636T=CGMCC 1.15388T).

Production of Lipopeptide Biosurfactant by a Marine Nesterenkonia sp. and Its Application in Food Industry

Biosurfactants are smart biomolecules which have wide spread application in medicines, processed foods, cosmetics as well as in bioremediation. In food industry, biosurfactants are used as emulsion stabilizing agents, antiadhesives, and antimicrobial/antibiofilm agents. Nowadays biosurfactant demands in industries has increased tremendously and therefore new bacterial strains are being explored for large scale production of biosurfactants. In this study, an actinobacterial strain MSA31 was isolated from a marine sponge Fasciospongia cavernosa which showed high activity in biosurfactant screening assays such as drop collapsing, oil displacement, lipase and emulsification. Lipopeptide produced by MSA31 was found to be thermostable which was evident in differential scanning calorimetry analysis. The spectral data obtained in the Fourier transform infrared spectroscopy showed the presence of aliphatic groups combined with peptide moiety which is a characteristic feature of lipopeptides. The stability index of lipopeptide MSA31 revealed “halo-alkali and thermal tolerant biosurfactant” which can be used in the food industry. Microtiter plate assay showed 125 μg/ml of lipopeptide was effective in reducing the biofilm formation activity of pathogenic multidrug resistant Staphylococcus aureus. The confocal laser scanning microscopic images provided further evidences that lipopeptide MSA31 was an effective antibiofilm agent. The antioxidant activity of lipopeptide MSA31 may be due to the presence of unsaturated fatty acid present in the molecule. The brine shrimp cytotoxicity assay showed lipopeptide MSA31 was non-toxic and can be used as food additives. Incorporation of lipopeptide MSA31 in muffin showed improved organoleptic qualities compared to positive and negative control. This study provides a valuable input for this lipopeptide to be used in food industry as an effective emulsifier, with good antioxidant activity and as a protective agent against S. aureus.

Genome Insight and Comparative Pathogenomic Analysis of Nesterenkonia jeotgali Strain CD08_7 Isolated from Duodenal Mucosa of Celiac Disease Patient

Species of the genus Nesterenkonia have been isolated from different ecological niches, especially from saline habitats and reported as weak human pathogens causing asymptomatic bacteraemia. Here, for the first time we are reporting the genome sequence and pathogenomic analysis of a strain designated as CD08_7 isolated from the duodenal mucosa of a celiac disease patient, identified as Nesterenkonia jeotgali. To date, only five strains of the genus Nesterenkonia (N. massiliensis strain NP1^T, Nesterenkonia sp. strain JCM 19054, Nesterenkonia sp. strain F and Nesterenkonia sp. strain AN1) have been whole genome sequenced and annotated. In the present study we have mapped and compared the virulence profile of N. jeotgali strain CD08_7 along with other reference genomes which showed some characteristic features that could contribute to pathogenicity. The RAST (Rapid Annotation using Subsystem Technology) based genome mining revealed more genes responsible for pathogenicity in strain CD08_7 when compared with the other four sequenced strains. The studied categories were resistance to antibiotic and toxic compounds, invasion and intracellular resistance, membrane transport, stress response, osmotic stress, oxidative stress, phages and prophages and iron acquisition. A total of 1431 protein-encoding genes were identified in the genome of strain CD08_7 among which 163 were predicted to contribute for pathogenicity. Out of 163 genes only 59 were common to other genome, which shows the higher levels of genetic richness in strain CD08_7 that may contribute to its functional versatility. This study provides a comprehensive analysis on genome of N. jeotgali strain CD08_7 and possibly indicates its importance as a clinical pathogen.

Nesterenkonia aurantiaca sp. nov., an alkaliphilic actinobacterium isolated from Antarctica

A Gram-stain-positive, non-endospore-forming, haloalkaliphilic actinobacterium, strain CK5^T, was isolated from a soil sample, collected at Cape King (Antarctica), and its taxonomic position was investigated by using a polyphasic approach. Cells were cocci with orange pigmentation, non-motile and grew optimally at 25 °C and pH 9.0-9.5 in the presence of 2 % (w/v) NaCl. Cellular membrane contained MK-7 (72 %) and MK-8 (28 %), and anteiso-C_15 : 0 (64.8 %), iso-C_16 : 0 (13.3 %), n-C_17 : 0 (9.9 %), n-C_16 : 0 (4.0 %), n-C_14 : 0 (3.7 %) as major cellular fatty acids. The DNA G+C content was 64.8 mol%. Strain CK5^T, based on the 16S rRNA gene sequence similarity, was most closely related to Nesterenkonia jeotgali JG-241^T (99.5 %), Nesterenkonia sandarakina YIM 70009^T (99.4 %), Nesterenkonia lutea YIM 70081^T (99.4 %), Nesterenkonia halotolerans YIM 70084^T (99.3 %), Nesterenkonia xinjiangensis YIM 70097^T (97.2 %), Nesterenkonia flava CAAS 251^T (97.1 %) and Nesterekonia aethiopica CCUG 48939^T (97.1 %). Strain CK5^T revealed 31 % DNA-DNA relatedness with respect to N. sandarakina DSM 15664^T, 29 % with respect to N. jeotgali DSM 19081^T, 10 % with respect to N. lutea DSM 15666^T and 1 % with respect to N. halotolerans, DSM 15474^T, N. xinjiangensis DSM 15475^T, N. aethiopica DSM 17733^T and N. flava DSM 19422^T. On the basis of 16S rRNA gene sequences, DNA-DNA hybridization and chemotaxonomic characteristics, strain CK5^T represents a novel species of the genus Nesterenkonia, for which the name Nesterenkonia aurantiaca sp. nov. is proposed. The type strain is CK5^T ( = DSM 27373^T = JCM 19723^T).

Thermophilic and alkaliphilic Actinobacteria: biology and potential applications

Microbes belonging to the phylum Actinobacteria are prolific sources of antibiotics, clinically useful bioactive compounds and industrially important enzymes. The focus of the current review is on the diversity and potential applications of thermophilic and alkaliphilic actinobacteria, which are highly diverse in their taxonomy and morphology with a variety of adaptations for surviving and thriving in hostile environments. The specific metabolic pathways in these actinobacteria are activated for elaborating pharmaceutically, agriculturally, and biotechnologically relevant biomolecules/bioactive compounds, which find multifarious applications.

Nesterenkonia populi sp. nov., an actinobacterium isolated from Populus euphratica

An alkaliphilic and moderately halophilic actinobacterium, designated strain GP10-3(T), was isolated from Populus euphratica collected from the southern edge of Taklimakan desert, Xinjiang, China. Cells of this strain were Gram-stain-positive, non-motile and non-spore-forming short rods. Strain GP10-3(T) grew optimally at 37 °C on LB agar media in the presence of 5-10% (w/v) NaCl at pH 9.0. The menaquinones were MK-7, MK-8 and MK-9. The major fatty acids (>10%) were anteiso-C17 : 0, anteiso-C15 : 0 and iso-C16 : 0. The peptidoglycan type was variation A4α, L-Lys-L-Glu. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylglycolipid, phosphatidylcholine, phosphatidylinositol, glycolipid and an unidentified phospholipid. The DNA G+C content was 67.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain GP10-3(T) belonged to the genus Nesterenkonia , sharing 94.6-96.9% sequence similarity with the type strains of species within this genus with validly published names. Based on the evidence of the polyphasic taxonomic study, strain GP10-3(T) represents a novel species of the genus Nesterenkonia , for which the name Nesterenkonia populi sp. nov. is proposed. The type strain is GP10-3(T) ( = DSM 27959(T) = KCTC 29119(T)).

Nesterenkonia alkaliphila sp. nov., an alkaliphilic, halotolerant actinobacteria isolated from the western Pacific Ocean

A Gram-staining-positive, aerobic, motile and non-spore-forming actinobacteria, designated strain F10T, was isolated from a deep-sea sediment of the western Pacific Ocean. Phylogenetic and phenotypic properties of the organism supported that it belonged to the genus Nesterenkonia . Strain F10T shared highest 16S rRNA gene sequence similarity of 96.8 % with Nesterenkonia aethiopica DSM 17733T, followed by Nesterenkonia xinjiangensis YIM 70097T (96.7 %) and Nesterenkonia alba CAAS 252T (96.6 %). The organism grew at 4–50 °C, at pH 7.0–12.0 and in the presence of 0–12 % (w/v) NaCl, with optimal growth occurring at 40 °C, at pH 9.0 and in the presence of 1 % (w/v) NaCl. The peptidoglycan type was A4(alpha), l-Lys–Gly–l-Glu. The polar lipid profile of strain F10T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, two unknown glycolipids and two unknown lipids. The isolate contained MK-9 (92 %) and MK-8 (5.8 %) as the major components of the menaquinone system, and anteiso-C17 : 0 (50.9 %) and anteiso-C15 : 0 (29.8 %) as the predominant fatty acids. The G+C content of the genomic DNA of strain F10T was 66.2 mol%. Based on phenotypic, genotypic and phylogenetic analyses, strain F10T represents a novel species of the genus Nesterenkonia for which the name Nesterenkonia alkaliphila sp. nov. is proposed. The type strain is F10T ( = LMG 28112T = CGMCC 1.12781T = JCM 19766T = MCCC 1A09946T).

Nesterenkonia rhizosphaerae sp. nov., an alkaliphilic actinobacterium isolated from rhizosphere soil in a saline-alkaline desert

An alkaliphilic actinobacterial strain, designated EGI 80099(T), was isolated from a rhizosphere soil sample of Reaumuria soongorica found in the desert soils of Fukang, Xinjiang, north-west China. Cells of strain EGI 80099(T) were Gram-stain-positive, non-motile, non-endospore-forming cocci. The predominant menaquinones were MK-7, MK-8 and MK-9. The major cellular fatty acids (>10 %) were anteiso-C15 : 0 and anteiso-C17 : 0. Analysis of the cell wall showed the presence of peptidoglycan of the type l-Lys-Gly-l-Glu, variation A4α. Cells of the isolate contained phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, an unknown phospholipid and an unidentified glycolipid as polar lipids. The genomic DNA G+C content was 63.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain EGI 80099(T) belongs to the genus Nesterenkonia, sharing 95.68-97.37 % sequence similarities with the type strains of recognized species within this genus. DNA-DNA hybridization of strain EGI 80099(T) with the type strains of species that showed the highest sequence similarities, Nesterenkonia aethiopica DSM 17733(T) (97.37 %), Nesterenkonia flava CAAS 251(T) (97.23 %) and Nesterenkonia xinjiangensis YIM 70097(T) (97.02 %), gave relatedness values of 8.7-62.2 %. Data from DNA-DNA hybridizations and physiological and biochemical tests indicated that strain EGI 80099(T) represents a novel species of the genus Nesterenkonia, for which the name Nesterenkonia rhizosphaerae sp. nov. is proposed. The type strain is EGI 80099(T) ( = BCRC 16947(T) = JCM 19129(T)).

Genome sequence and description of Nesterenkonia massiliensis sp. nov. strain NP1(T.)

Nesterenkonia massiliensis sp. nov., strain NP1^T, is the type strain of Nesterenkonia massiliensis sp. nov., a new species within the genus Nesterenkonia. This strain, whose genome is described here, was isolated from the feces of a 32-year-old French woman suffering from AIDS and living in Marseille. Nesterenkonia massiliensis is a Gram-positive aerobic coccus. Here, we describe the features of this bacterium, together with the complete genome sequencing and annotation. The 2,726,371 bp long genome (one chromosome but no plasmid) contains 2,663 protein-coding and 51 RNA genes, including 1 rRNA operon.

Novel marine actinobacteria from emerald Andaman & Nicobar Islands: a prospective source for industrial and pharmaceutical byproducts

BACKGROUND

Andaman and Nicobar Islands situated in the eastern part of Bay of Bengal are one of the distinguished biodiversity hotspot. Even though number of studies carried out on the marine flora and fauna, the studies on actinobacteria from Andaman and Nicobar Islands are meager. The aim of the present study was to screen the actinobacteria for their characterization and identify the potential sources for industrial and pharmaceutical byproducts.

RESULTS

A total of 26 actinobacterial strains were isolated from the marine sediments collected from various sites of Port Blair Bay where no collection has been characterized previously. Isolates were categorized under the genera: Saccharopolyspora, Streptomyces, Nocardiopsis, Streptoverticillium, Microtetraspora, Actinopolyspora, Actinokineospora and Dactylosporangium. Majority of the isolates were found to produce industrially important enzymes such as amylase, protease, gelatinase, lipase, DNase, cellulase, urease and phosphatase, and also exhibited substantial antibacterial activity against human pathogens. 77% of isolates exhibited significant hemolytic activity. Among 26 isolates, three strains (NIOT-VKKMA02, NIOT-VKKMA22 and NIOT-VKKMA26) were found to generate appreciable extent of surfactant, amylase, cellulase and protease enzyme. NIOT-VKKMA02 produced surfactant using kerosene as carbon source and emulsified upto E(24)-63.6%. Moreover, NIOT-VKKMA02, NIOT-VKKMA22 and NIOT-VKKMA26 synthesized 13.27 U/ml, 9.85 U/ml and 8.03 U/ml amylase; 7.75 U/ml, 5.01 U/ml and 2.08 U/ml of cellulase and 11.34 U/ml, 6.89 U/ml and 3.51 U/ml of protease enzyme, respectively.

CONCLUSIONS

High diversity of marine actinobacteria was isolated and characterized in this work including undescribed species and species not previously reported from emerald Andaman and Nicobar Islands, including Streptomyces griseus, Streptomyces venezuelae and Saccharopolyspora salina. The enhanced salt, pH and temperature tolerance of the actinobacterial isolates along with their capacity to secrete commercially valuable primary and secondary metabolites emerges as an attractive feature of these organisms. These results are reported for the first time from these emerald Islands and expand the scope to functionally characterize novel marine actinobacteria and their metabolites for the potential novel molecules of commercial interest.

Nesterenkonia suensis sp. nov., a haloalkaliphilic actinobacterium isolated from a salt pan

A Gram-positive, non-motile, non-spore-forming actinobacterium designated strain Sua-BAC020T was isolated from brine from Sua salt pan in Botswana. The strain was alkaliphilic and moderately halophilic, displaying optimal growth at 35–37 °C, pH 9 and 2.5 % (w/v) NaCl. Comparative 16S rRNA gene sequence analysis showed that strain Sua-BAC020T belonged to the genus Nesterenkonia , sharing 96.2–99.0 % sequence similarity with the type strains of recognized species within this genus. DNA–DNA hybridization with the type strains of species that showed the closest phylogenetic affiliation, Nesterenkonia xinjiangensis (16S rRNA gene sequence similarity, 98.9 %), Nesterenkonia aethiopica (99.0 %), Nesterenkonia halophila (97.5 %), Nesterenkonia flava (97.4 %) and Nesterenkonia halobia (97.2 %), gave relatedness values of 10–45 %. The peptidoglycan type of strain Sua-BAC020T was A4α, l-Lys–Gly–d-Asp. Cells of the isolate contained phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol and unidentified glycolipids as major polar lipids, MK-8, MK-9 and MK-7 were the predominant menaquinones, and the major fatty acids (>10 %) were anteiso-C15 : 0 and anteiso-C17 : 0. The DNA G+C content of strain Sua-BAC020T was 64.8 mol%. Based on DNA–DNA hybridization, and physiological and biochemical tests, strain Sua-BAC020T is distinct from all recognized Nesterenkonia species, suggesting that this strain represents a novel species, for which the name Nesterenkonia suensis sp. nov. is proposed. The type strain is Sua-BAC020T ( = DSM 22748T = NCCB 100309T).

Systematic and biotechnological aspects of halophilic and halotolerant actinomycetes

More than 70 species of halotolerant and halophilic actinomycetes belonging to at least 24 genera have been validly described. Halophilic actinomycetes are a less explored source of actinomycetes for discovery of novel bioactive secondary metabolites. Degradation of aliphatic and aromatic organic compounds, detoxification of pollutants, production of new enzymes and other metabolites such as antibiotics, compatible solutes and polymers are other potential industrial applications of halophilic and halotolerant actinomycetes. Especially new bioactive secondary metabolites that are derived from only a small fraction of the investigated halophilic actinomycetes, mainly from marine habitats, have revealed the huge capacity of this physiological group in production of new bioactive chemical entities. Combined high metabolic capacities of actinomycetes and unique features related to extremophilic nature of the halophilic actinomycetes have conferred on them an influential role for future biotechnological applications.