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.

Saccharopolyspora spongiae sp. nov., a novel actinomycete isolated from the marine sponge Scopalina ruetzleri (Wiedenmayer, 1977)

A novel marine actinomycete, designated strain CMAA 1452T, was isolated from the sponge Scopalina ruetzleri collected from Saint Peter and Saint Paul Archipelago, in Brazil, and subjected to a polyphasic taxonomic investigation. The organism formed a distinct phyletic line in the Saccharopolyspora 16S rRNA gene tree and had chemotaxonomic and morphological properties consistent with its classification in this genus. It was found to be closely related to Saccharopolyspora dendranthemae KLBMP 1305T (99.5% 16S rRNA gene sequence similarity) and shared similarities of 99.3, 99.2 and 99.0 % with 'Saccharopolyspora endophytica' YIM 61095, Saccharopolyspora tripterygii YIM 65359T and 'Saccharopolyspora pathumthaniensis' S582, respectively. DNA-DNA relatedness values between the isolate and its closest phylogenetic neighbours, namely S. dendranthemae KLBMP 1305T, 'S. endophytica' YIM 61095 and S. tripterygii YIM 65359T, were 53.5, 25.8 and 53.2 %, respectively. Strain CMAA 1452T was also distinguished from the type strains of these species using a range of phenotypic features. On the basis of these results, it is proposed that strain CMAA 1452T (=DSM 103218T=NRRL B-65384T) merits recognition as the type strain of a novel Saccharopolyspora species, Saccharopolyspora spongiae sp. nov.

Haloactinomyces albus gen. nov., sp. nov., isolated from the Dead Sea

A novel halophilic, filamentous actinomycete strain, designated AFM 10258T, was isolated from a sediment sample collected from the Dead Sea of Israel. The isolate grew with 10-35 % NaCl and did not grow without NaCl. The isolate formed white aerial mycelium and long spore chains, and two spores were separated by sterile mycelium. The spores were non-motile, spherical and rugose-surfaced. The isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and galactose and arabinose as the major whole-cell sugars. The polar lipids were diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and three unknown phospholipids. Major fatty acids were anteiso-C17 : 0, iso-C16 : 0 and iso-C15 : 0. MK-9(H4) was the predominant menaquinone and the DNA G+C content was 62.8 mol%. 16S rRNA gene sequence analysis indicated that strain AFM 10258T shared low sequence similarity with the closely related representatives of the families Pseudonocardiaceae (below 94.47 %) and Actinopolysporaceae (below 93.76 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AFM 10258T formed a robust clade with members of the family Actinopolysporaceae. On the basis of analysis of phenotypic, chemical and molecular characteristics, strain AFM 10258T is considered to represent a novel species of a new genus, for which the name Haloactinomyces albus gen. nov., sp. nov., is proposed. The type strain is AFM 10258T (=DSM 45977T=CGMCC 4.7115T).

Saccharopolyspora griseoalba sp. nov., a novel actinomycete isolated from the Dead Sea

A novel halotolerant actinomycete, designated strain AFM 10238^T, was isolated from a sediment sample collected from the Dead Sea of Israel. The isolate grew at 15-45 °C, pH 6-12 and with 0-15 % (w/v) NaCl. Strain AFM 10238^T contains meso-diaminopimelic acid as cell wall diamino acid, and galactose and arabinose as the whole cell sugars. The major polar lipids are phosphatidylcholine, phosphatidylglycerol, and diphosphatidylglycerol. Major fatty acids are iso-C_16:0, iso-C_17:0, iso-C_15:0, anteiso-C_17:0 and C_17:1 ω8c. MK-9(H₄) is the predominant menaquinone and the DNA G + C content is 72.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AFM10238^T belongs to the genus Saccharopolyspora. The 16S rRNA gene sequence similarity between strain AFM 10238^T and its close neighbours, Saccharopolyspora halophila YIM 90500^T , Saccharopolyspora spinosa DSM 44228^T, Saccharopolyspora dendranthemae KLBMP 1305^T and Saccharopolyspora cebuensis DSM 45019^T were 98.2, 97.2, 97.1 and 97.0 %, respectively. Sequence similarities to other type strains of this genus were below 97 %. DNA-DNA relatedness data, together with phenotypic and chemotaxonomic differences, clearly distinguished the isolate from its close neighbours. On the basis of the data from this polyphasic analysis, a novel species Saccharopolyspora griseoalba sp. nov. is proposed. The type strain is AFM 10238^T (= DSM 46,663 = CGMCC 4.7124).

Unmasking the measles-like parchment discoloration: molecular and microanalytical approach

Many ancient parchments are defaced by red or purple maculae associated with localized destruction of collagen fibres. Although the main characteristics of this damage were present in most of the manuscripts analysed by many authors, no common microbial or fungal denominator has been found so far, and little or no correspondence between the microbial or fungal species isolated from materials could be addressed. In this study, culture-independent molecular methods and scanning electron microscopy (SEM) were used to identify fungal and bacterial communities on parchments affected by the purple stains. Protocols for c extraction and nucleic-acid-based strategies were selected for assays examining the community structure of fungi and bacteria on biodeteriorated parchment. Both SEM and molecular analysis detected the presence of bacterial and fungal cells in the damaged areas. Halophilic, halotolerant proteolytic bacterial species were selected by the saline environment provided by the parchment samples. As common microbial denominators, members of the Actinobacteria, mainly Saccharopolyspora spp. and species of Aspergillus, were detected in all investigated cases. It is proposed that a relationship exists between the phenomenon of purple spots on ancient parchments and that of the 'red heat' phenomenon, known to be present in some products manufactured with marine salt.

Saccharopolyspora halotolerans sp. nov., a halophilic actinomycete isolated from a hypersaline lake

A novel actinomycete strain, designated TRM 45123T, was isolated from a hypersaline habitat in Xinjiang Province (40° 20′ N 90° 49′ E), north-west China. The isolate was characterized using a polyphasic approach. 16S rRNA gene sequence analysis indicated that strain TRM 45123T belonged to the genus Saccharopolyspora and was closely related to Saccharopolyspora gloriosae (96.7 % similarity). The G+C content of the DNA was 69.07 mol%. The isolate contained meso-diaminopimelic acid as the diagnostic diamino acid, and arabinose and ribose as the major whole-cell sugars. The diagnostic phospholipids were phosphatidylethanolamine, phosphatidylcholine and phosphatidylglycerol. The predominant menaquinone was MK-9(H4). The major fatty acids were iso-C16 : 0, anteiso-C17 : 0, iso-C15 : 0 and anteiso-C15 : 0. On the basis of the evidence from this polyphasic study, a novel species, Saccharopolyspora halotolerans sp. nov., is proposed. The type strain of Saccharopolyspora halotolerans is TRM 45123T ( = CCTCC AA 2013006T = DSM 45990T).

Mzabimyces algeriensis gen. nov., sp. nov., a halophilic filamentous actinobacterium isolated from a Saharan soil, and proposal of Mzabimycetaceae fam. nov

Three halophilic mycelium-forming actinobacteria, strains H195(T), H150 and H151, were isolated from a Saharan soil sample collected from Béni-isguen in the Mzab region (Ghardaïa, South of Algeria) and subjected to a polyphasic taxonomic characterisation. These strains were observed to show an aerial mycelium differentiated into coccoid spore chains and fragmented substrate mycelium. Comparative analysis of the 16S rRNA gene sequences revealed that the highest sequence similarities were to Saccharopolyspora qijiaojingensis YIM 91168(T) (92.02 % to H195(T)). Phylogenetic analyses showed that the strains H195(T), H150 and H151 represent a distinct phylogenetic lineage. The cell-wall hydrolysate was found to contain meso-diaminopimelic acid, and the diagnostic whole-cell sugars were identified as arabinose and galactose. The major cellular fatty acids were identified as iso-C15:0, iso-C16:0, iso-C17:0 and anteiso-C17:0. The diagnostic phospholipid detected was phosphatidylcholine and MK-9 (H4) was found to be the predominant menaquinone. The genomic DNA G+C content of strain H195(T) was 68.2 mol%. On the basis of its phenotypic features and phylogenetic position, we propose that strain H195(T) represents a novel genus and species, Mzabimyces algeriensis gen. nov., sp. nov., within a new family, Mzabimycetaceae fam. nov. The type strain of M. algeriensis is strain H195(T) (=DSM 46680(T) = MTCC 12101(T)).

Saccharopolyspora indica sp. nov., an actinomycete isolated from the rhizosphere of Callistemon citrinus (Curtis)

A novel actinomycete strain, designated VRC122T, was isolated from a Callistemon citrinus rhizosphere sample collected from New Delhi, India, and its taxonomic status was determined by using a polyphasic approach. Strain VRC122T was a Gram-stain-positive, aerobic, non-motile, non-acid–alcohol-fast strain. Phylogenetic analysis based on 16S rRNA gene sequences showed the strain was placed in a well-separated sub-branch within the genus Saccharopolyspora . The highest levels of 16S rRNA gene sequence similarity were found with Saccharopolyspora hirsuta subsp. kobensis JCM 9109T (98.71 %), Saccharopolyspora antimicrobica I05-00074T (98.69 %) and Saccharopolyspora jiangxiensis W12T (98.66 %); 16S rRNA gene sequence similarities with type strains of all other species of the genus Saccharopolyspora were below 98 %. Chemosystematic studies revealed that it contained meso-diaminopimelic acid. Arabinose and galactose were the predominant whole-cell sugars. Diagnostic polar lipids were diphosphatidylglycerol, phosphatidylinositol and phosphatidylcholine. MK-9(H6) was the predominant menaquinone. C14 : 0, C16 : 0, iso-C15 : 0, iso-C16 : 0, iso-C17 : 0, anteiso-C15 : 0, anteiso-C17 : 0, C17 : 0 cyclo and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) were the major cellular fatty acids. The G+C content of the genomic DNA was 69.5 mol%. The results of DNA–DNA hybridization (30 %, 22 % and 25 %, respectively) with type strains of the above-mentioned species, in combination with differences in physiological and biochemical data supported that strain VRC122T represents a novel species of the genus Saccharopolyspora , for which the name Saccharopolyspora indica sp. nov., is proposed. The type strain is VRC122T ( = KCTC 29208T = MTCC 11564T = MCC 2206T = ATCC BAA-2551T).

Saccharopolyspora ghardaiensis sp. nov., an extremely halophilic actinomycete isolated from Algerian Saharan soil

A novel halophilic actinomycete, strain designated H53(T), was isolated from a Saharan soil sample collected from Chaâbet Ntissa, Béni-isguen, Ghardaïa (South of Algeria) and was characterized taxonomically by means of polyphasic approach. Optimal growth was found to occur at 30-35 °C, pH 6-7 and in the presence of 15-25% (w/v) NaCl. The strain was observed to produce abundant aerial mycelium, which formed long chains of rod-shaped spores at maturity, and well developed and fragmented substrate mycelium. The cell wall was determined to contain meso-diaminopimelic acid; the diagnostic whole-cell sugars were arabinose and galactose. The predominant menaquinones were found to be MK-9(H₄) and MK-9(H₆). The predominant cellular fatty acids were determined to be iso- and anteiso-C17:0, iso-C15:0, and cis9 iso-C17:1. The diagnostic phospholipid detected was phosphatidylcholine. The morphological and chemotaxonomic characteristics of the strain were consistent with those of members of the genus Saccharopolyspora. Phylogenetic analyses on the basis of the 16S ribosomal RNA (rRNA) gene sequence showed that this strain formed a distinct phyletic line within the radiation of the genus Saccharopolyspora. The 16S rRNA sequence similarities between strain H53(T) and other members of the genus Saccharopolyspora ranged from 92.1 to 94.3%. The DNA G+C content of strain H53(T) was 72.6%. The genotypic and phenotypic data showed that the strain H53(T) represents a novel species of the genus Saccharopolyspora, for which the name Saccharopolyspora ghardaiensis sp. nov. is proposed, with the type strain H53(T) (=DSM 45606(T)=CCUG 63370(T)=CECT 8304(T)).

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.

Saccharopolyspora pathumthaniensis sp. nov., a novel actinomycetes isolated from termite guts (Speculitermes sp.)

Morphological and chemotaxonomic characterization of actinomycete strain S582 isolated from the gut of a termite (Speculitermes sp.) in Pathum Thani Province, Thailand, clearly demonstrated that this strain is a member of the genus Saccharopolyspora. 16S rDNA sequence analysis for the strain supported the assignment of the strain to the genus Saccharopolyspora. The similarity value of sequences between this strain and the closely related species Saccharopolyspora endophytica was 99.5%. The DNA G+C content was 70.2 mol%. DNA-DNA hybridization results (53.3%) and some physiological and biochemical properties indicated that strain S582(T) was distinguished from the phylogenetically closest relatives. Based on these genotypic and phenotypic data, strain S582(T) should be a new species in the genus Saccharopolyspora and the name Saccharopolyspora pathumthaniensis sp. nov. is proposed for the strain. The type strain is S582(T) (=NBRC 104112(T) =BCC 28624(T)).

Bioprospecting microbial natural product libraries from the marine environment for drug discovery

Marine microorganisms are fascinating resources due to their production of novel natural products with antimicrobial activities. Increases in both the number of new chemical entities found and the substantiation of indigenous marine actinobacteria present a fundamental difficulty in the future discovery of novel antimicrobials, namely dereplication of those compounds already discovered. This review will share our experience on the taxonomic-based construction of a highly diversified and low redundant marine microbial natural product library for high-throughput antibiotic screening. We anticipate that libraries such as these can drive the drug discovery process now and in the future.

Saccharopolyspora gloriosae sp. nov., an endophytic actinomycete isolated from the stem of Gloriosa superba L

A Gram-stain-positive, aerobic actinomycete, strain YIM 60513T, was isolated from the stem of Gloriosa superba L. collected from tropical rainforest at Xishuangbanna, Yunnan Province, south-west China. 16S rRNA gene sequence analysis indicated that strain YIM 60513T belonged to the genus Saccharopolyspora and was closely related to Saccharopolyspora gregorii NCIB 12823T (99.1 % similarity) and Saccharopolyspora cebuensis SPE 10-1T (97.3 % similarity). Data for the predominant quinone [MK-9(H4)], major fatty acids (iso-C16 : 0, anteiso-C17 : 0 and C17 : 1 cis9) and G+C content of the genomic DNA (71.6 mol%) were similar to those for members of the genus Saccharopolyspora. The level of DNA–DNA relatedness between strain YIM 60513T and S. gregorii NCIB 12823T was 43 %. The combination of phylogenetic analysis, phenotypic differences, chemotaxonomic characteristics and DNA–DNA hybridization data supported the view that strain YIM 60513T should be distinguished from S. gregorii NCIB 12823T and S. cebuensis SPE 10-1T. Strain YIM 60513T therefore represents a novel species of the genus Saccharopolyspora, for which the name Saccharopolyspora gloriosae sp. nov. is proposed. The type strain is YIM 60513T (=KCTC 19243T =CCTCC AA 207006T).

Haloechinothrix alba gen. nov., sp. nov., a halophilic, filamentous actinomycete of the suborder Pseudonocardineae

A novel halophilic, filamentous actinomycete strain, designated YIM 93221(T), was isolated from a salt lake in Xinjiang province, north-west China, and subjected to a polyphasic taxonomic characterization. The isolate grew with 9-23 % (w/v) NaCl and did not grow without NaCl. The isolate formed spiny aerial mycelium and did not form spores at maturity. The isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and glucose, glucosamine, mannose and an unknown sugar as the major whole-cell sugars. The phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannosides and an unknown phospholipid. MK-8(H(4)) was the predominant menaquinone. The major fatty acid was iso-C(16 : 0). The DNA G+C content was 68.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YIM 93221(T) formed a distinct lineage within the suborder Pseudonocardineae and showed 91.9-94.8 % 16S rRNA gene sequence similarity with members of the suborder Pseudonocardineae. On the basis of the evidence from this polyphasic study, a novel genus and species, Haloechinothrix alba gen. nov., sp. nov., are proposed. The type strain of Haloechinothrix alba is YIM 93221(T) (=DSM 45207(T) =CCTCC AB 208140(T)).