Actinobacterial diversity from marine sediments collected in Mexico

Seventeen different media known to support the growth and isolation of members of the class Actinobacteria were evaluated as selective isolation media for the recovery of this microbial group from marine sediments samples collected in the Gulf of California and the Gulf of Mexico. A general selective isolation procedure was employed for six sediments and nearly 300 actinomycetes were recovered from the selective isolation plates. Full 16S rRNA gene sequencing revealed that the isolates belonged to several actinobacterial taxa, notably to the genera Actinomadura, Dietzia, Gordonia, Micromonospora, Nonomuraea, Rhodococcus, Saccharomonospora, Saccharopolyspora, Salinispora, Streptomyces, “Solwaraspora” and Verrucosispora. Previous works on marine sediments have been restricted to the isolation of members of the genera Micromonospora, Rhodococcus and Streptomyces. This study provides further evidence that Actinobacteria present in marine habitats are not restricted to the Micromonospora-Rhodococcus-Streptomyces grouping. Indeed, this first systematic study shows the extent of actinobacterial diversity that can be found in marine sediments collected in Mexico and probably, worldwide. The 16S rRNA gene sequences of marine isolates A1, AA2, AA6, AB1, AB2, AG1, AI2, AK1, AL2, AO1, AO3, AR1, AW1, B1, BB1, BC1, C5, R1, R2, R3, AV1, AE1, AI1, AN1 and AP1 determined in this study have been deposited under GenBank accession numbers EU714241–EU714258 and FJ462359–FJ462365, respectively.     

青藏高原阿里、那曲和海西地区土壤可培养放线菌的多样性

【目的】为了研究青藏高原北部地区土壤可培养放线菌的多样性,并比较不同选择性分离培养基对高原土壤放线菌的分离效果。【方法】使用9种分离培养基,并尝试添加藤黄微球菌发酵液,对采集自阿里、那曲和海西地区的14份土壤样品中的放线菌进行选择性分离。通过16S r RNA基因序列分析对分离菌株进行初步分类鉴定,并在不同分类水平上统计所分离得到的放线菌多样性。【结果】分离得到去重复后的放线菌255株,分布于放线菌门的8个目,14个科,23个属,包含94个可能的物种。其中至少25个物种可能为新种,分布于13个属。链霉菌属的菌株108株,可能的物种28个,是最主要的优势菌属。分离培养基中添加藤黄微球菌发酵液明显增加了放线菌分离菌株的数量和多样性,稀释的葡萄糖酵母麦芽汁培养基适合分离链霉菌,淀粉甘油脯氨酸培养基、丙酸钠酪蛋白培养基等则适合分离稀有放线菌。【结论】青藏高原北部土壤放线菌多样性非常丰富,并且存在较多的新颖放线菌类群;添加藤黄微球菌发酵液是提高放线菌分离效率的有效手段。     

A comparative study on the phylogenetic diversity of culturable actinobacteria isolated from five marine sponge species

A cultivation-based approach was employed to compare the culturable actinobacterial diversity associated with five marine sponge species (Craniella australiensis, Halichondria rugosa, Reniochalina sp., Sponge sp., and Stelletta tenuis). The phylogenetic affiliation of the actinobacterial isolates was assessed by 16S rDNA-RFLP analysis. A total of 181 actinobacterial strains were isolated using five different culture media (denoted as M1–M5). The type of medium exhibited significant effects on the number of actinobacteria recovered, with the highest number of isolates on M3 (63 isolates) and the lowest on M1 (12 isolates). The genera isolated were also different, with the recovery of three genera on M2 and M3, and only a single genus on M1. The number of actinobacteria isolated from the five sponge species was significantly different, with a count of 83, 36, 30, 17, and 15 isolates from S. tenuis, H. rugosa, Sponge sp., Reniochalina sp., and C. australiensis, respectively. M3 was the best isolation medium for recovery of actinobacteria from S. tenuis, H. rugosa, and Sponge sp., while no specific medium preference was observed for the recovery of actinobacteria from Reniochalina sp., and C. australiensis. The RFLP fingerprinting of 16S rDNA genes digested with HhaI revealed six different patterns, in which 16 representative 16S rDNAs were fully sequenced. Phylogenetic analysis indicated that 12 strains belong to the group Streptomyces, three strains belong to Pseudonocardia, and one strain belongs to Nocardia. Two strains C14 (from C. australiensis) and N13 (from Sponge sp.) have only 96.26% and 96.27% similarity to earlier published sequences, and are therefore potential candidates for new species. The highest diversity of three actinobacteria genera was obtained from Sponge sp., though the number of isolates was low. Two genera of actinobacteria, Streptomyces, and Pseudonocardia, were isolated from both S. tenuis and C. australiensis. Only the genus of Streptomyces was isolated from H. rugosa and Reniochalina sp. Sponge species have been demonstrated here to vary as sources of culturable actinobacterial diversity, and the methods for sampling such diversity presented may be useful for improved sampling of such diversity.     

Unique Microbial Signatures of the Alien Hawaiian Marine Sponge Suberites zeteki

Invasive species poses a threat to the world’s oceans. Alien sponges account for the majority of introduced marine species in the isolated Hawaiian reef ecosystems. In this study, cultivation-dependent and cultivation-independent techniques were applied to investigate microbial consortia associated with the alien Hawaiian marine sponge Suberites zeteki. Its microbial communities were diverse with representatives of Actinobacteria, Firmicutes, α- and γ-Proteobacteria, Bacteroidetes, Chlamydiae, Planctomycetes, and Cyanobacteria. Specifically, the genus Chlamydia was identified for the first time from marine sponges, and two genera (Streptomyces and Rhodococcus) were added to the short list of culturable actinobacteria from sponges. Culturable microbial communities were dominated by Bacillus species (63%) and contained actinobacterial species closely affiliated with those from habitats other than marine sponges. Cyanobacterial clones were clustered with free-living cyanobacteria from water column and other environmental samples; they show no affiliation with other sponge-derived cyanobacteria. The low sequence similarity of Planctomycetes, Chlamydiae, and α-Proteobacteria clones to other previously described sequences suggested that S. zeteki may contain new lineages of these bacterial groups. The microbial diversity of S. zeteki was different from that of other studied marine sponges. This is the first report on microbial communities of alien marine invertebrate species. For the first time, it provides an insight into microbial structure within alien marine sponges in the Hawaiian marine ecosystems.     

Culturable rare Actinomycetes: diversity, isolation and marine natural product discovery

Rare Actinomycetes from underexplored marine environments are targeted in drug discovery studies due to the Actinomycetes’ potentially huge resource of structurally diverse natural products with unusual biological activity. Of all marine bacteria, 10 % are Actinomycetes, which have proven an outstanding and fascinating resource for new and potent bioactive molecules. Past and present efforts in the isolation of rare Actinomycetes from underexplored diverse natural habitats have resulted in the isolation of about 220 rare Actinomycete genera of which more than 50 taxa have been reported to be the producers of 2,500 bioactive compounds. That amount represents greater than 25 % of the total Actinomycetes metabolites, demonstrating that selective isolation methods are being developed and extensively applied. Due to the high rediscovery rate of known compounds from Actinomycetes, a renewed interest in the development of new antimicrobial agents from rare and novel Actinomycetes is urgently required to combat the increasing number of multidrug-resistant human pathogens. To facilitate that discovery, this review updates all selective isolation media including pretreatment and enrichment methods for the isolation of marine rare Actinomycetes. In addition, this review demonstrates that discovering new compounds with novel scaffolds can be increased by intensive efforts in isolating and screening rare marine genera of Actinomycetes. Between 2007 and mid-2013, 80 new rare Actinomycete species were reported from marine habitats. They belong to 23 rare families, of which three are novel, and 20 novel genera. Of them, the family Micromonosporaceae is dominant as a producer of promising chemical diversity.     

Rational Approaches to Improving the Isolation of Endophytic Actinobacteria from Australian Native Trees

In recent years, new actinobacterial species have been isolated as endophytes of plants and shrubs and are sought after both for their role as potential producers of new drug candidates for the pharmaceutical industry and as biocontrol inoculants for sustainable agriculture. Molecular-based approaches to the study of microbial ecology generally reveal a broader microbial diversity than can be obtained by cultivation methods. This study aimed to improve the success of isolating individual members of the actinobacterial population as pure cultures as well as improving the ability to characterise the large numbers obtained in pure culture. To achieve this objective, our study successfully employed rational and holistic approaches including the use of isolation media with low concentrations of nutrients normally available to the microorganism in the plant, plating larger quantities of plant sample, incubating isolation plates for up to 16 weeks, excising colonies when they are visible and choosing Australian endemic trees as the source of the actinobacteria. A hierarchy of polyphasic methods based on culture morphology, amplified 16S rRNA gene restriction analysis and limited sequencing was used to classify all 576 actinobacterial isolates from leaf, stem and root samples of two eucalypts: a Grey Box and Red Gum, a native apricot tree and a native pine tree. The classification revealed that, in addition to 413 Streptomyces spp., isolates belonged to 16 other actinobacterial genera: Actinomadura (two strains), Actinomycetospora (six), Actinopolymorpha (two), Amycolatopsis (six), Gordonia (one), Kribbella (25), Micromonospora (six), Nocardia (ten), Nocardioides (11), Nocardiopsis (one), Nonomuraea (one), Polymorphospora (two), Promicromonospora (51), Pseudonocardia (36), Williamsia (two) and a novel genus Flindersiella (one). In order to prove novelty, 12 strains were characterised fully to the species level based on polyphasic taxonomy. One strain represented a novel genus in the family Nocardioides, and the other 11 strains were accepted as novel species. In summary, the holistic isolation strategies were successful in obtaining significant culturable actinobacterial diversity within Australian native trees that includes rare and novel species.     

Isolation,Classification and Antagonistic Properties of Alkalitolerant Actinobacteria from Algerian Saharan Soils

Abstract

The Sahara, one of the most extreme environments on Earth, constitutes an unexplored source of alkalitolerant actinobacteria. In this work, we studied the diversity of alkalitolerant actinobacteria in various soils collected from different regions of the Algerian Sahara. A total of 29 alkalitolerant actinobacterial strains were isolated by using a complex agar medium. The diversity of these actinobacteria was evaluated using a polyphasic approach, which included morphological, chemotaxonomic, physiological (numerical taxonomy) and 16S rRNA gene analyses. The isolates which were assigned to the genus Nocardiopsis, shared relatively low 16S rRNA gene sequences similarities compared to closely related species suggesting that they belonged to putatively new species. All of the strains were tested for antibiotic activity against a broad range of microorganisms and screened for genes encoding polyketide synthases and non-ribosomal peptide synthetases and found to have the potential to produce secondary metabolites. Consequently, the study supports the view that extreme environments contain many novel actinobacteria, which represent an unexplored source for the discovery of biologically active compounds.     

一份南海深海沉积物样品中可培养细菌的多样性

海洋沉积环境蕴含丰富的微生物资源。对深海难培养微生物的分离培养,不仅有利于深海微生物资源的挖掘与利用,也有利于对深海微生物学的研究。本研究采用多种培养基分离获得细菌菌株纯培养,并通过16S r RNA基因序列鉴定,对我国南海海域1个4 000 m水深的深海表层沉积物样品的可培养细菌多样性进行初探。共设计23种分离培养基,经过选择性分离培养最终获得612株细菌菌株,分别隶属于厚壁菌门(Firmicutes)、放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes)的9目10科27个属级类群,可培养优势类群为厚壁菌门,占所有分离物种数量的85.8%,包含13个16S rRNA基因序列相似性低于98%的潜在新物种。海洋琼脂类培养基适合培养不同种类的海洋细菌类群,放线菌选择性分离类合成培养基对放线菌类群的分离效果较好。最终获得一些与具有产抗生素、细胞毒素、高效酶活、耐受不良环境、降解污染物等特殊功能微生物相近的菌株。研究结果表明,该深海沉积物样品的可培养微生物资源、潜在新物种和微生物生理特性丰富多样,研究深海环境难培养微生物的分离策略及其微生物适应生理特性对研究极端环境微生物打下了基础。     

Diversity and novelty of actinobacteria in Arctic marine sediments

The actinobacterial diversity of Arctic marine sediments was investigated using culture-dependent and culture-independent approaches. A total of 152 strains were isolated from seven different media; 18 isolates were selected for phylogenetic analysis on the basis of their 16S rRNA gene sequences. Results showed that the 18 isolates belonged to a potential novel genus and 10 known genera including Actinotalea, Arthrobacter, Brachybacterium, Brevibacterium, Kocuria, Kytococcus, Microbacterium, Micrococcus, Mycobacterium, and Pseudonocardia. Subsequently, 172 rDNA clones were selected by restriction fragment length polymorphism analysis from 692 positive clones within four actinobacteria-specific 16S rDNA libraries of Arctic marine sediments, and then these 172 clones were sequenced. In total, 67 phylotypes were clustered in 11 known genera of actinobacteria including Agrococcus, Cellulomonas, Demequina, Iamia, Ilumatobacter, Janibacter, Kocuria, Microbacterium, Phycicoccus, Propionibacterium, and Pseudonocardia, along with other, unidentified actinobacterial clones. Based on the detection of a substantial number of uncultured phylotypes showing low BLAST identities (<95 %), this study confirms that Arctic marine environments harbour highly diverse actinobacterial communities, many of which appear to be novel, uncultured species.     

Diversity of Actinobacterial community in saline sediments from Yunnan and Xinjiang, China

The diversity and community structures of actinobacteria in saline sediments collected from Yunnan and Xinjiang Provinces, China, were investigated with cultivation and 16S rRNA gene analysis. A total of 163 actinobacterial isolates were obtained, and they were affiliated with the order Actinomycetales (distributed into five suborders: Streptosporangineae, Micrococcineae, Streptomycineae, Pseudonocardineae, and Glycomycineae). A total of 748 actinobacterial 16S rRNA gene clones were examined, and they could be classified into Actinomycetales, Acidimicrobiales, and unclassified actinobacteria. The Actinomycetales sequences were distributed into nine suborders: Streptosporangineae, Glycomycineae, Micromonosporineae, Pseudonocardineae, Corynebacterineae, Frankineae, Propionibacterineae, Streptomycineae, and Micrococcineae. The unclassified actinobacteria contained three new clusters at the level of subclass or order. Our 16S rRNA gene phylogenetic data indicated that actinobacterial communities were very diverse in the investigated saline sediments (salinity 0.4–11.6%) and some actinobacterial members may be halotolerant or halophilic. The actinobacterial community structures in the saline sediments were different from those in marine and freshwater environments. Our data have implications for a better understanding of the distribution of Actinobacteria in saline environments. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Use of phage battery to investigate the actinofloral layers of termite gut microflora

AIMS: The termite gut microbiota can include a variety of micro-organisms from the three domains: Bacteria, Archaea and Eucarya. The bacterial groups from the gut systems are mainly affiliated to the proteobacteria, the Gram-positive groups Bacterioiodes/Flavobacterium branch and the spirochetes, Firmicutes and Actinobacteria. However, culture independent molecular studies have revealed that the majority of these microbial gut symbionts have not yet been cultured, including actinobacterial clusters associated with termite guts. Accordingly, the aim of this study was to selectively isolate the actinofloral layers of gut associated microflora of the Coptotermes lacteus (Froggatt) species located at the Sunshine Coast Region of Queensland, Australia to increase our knowledge on the diversity of actinobacterial taxa present in the termite guts. METHODS AND RESULTS: Actinofloral layers associated with the guts of the wood-eating subterranean termite C. lacteus were investigated by exploiting the phage susceptibility of different gut associated bacteria which impede the growth of actinomycetes on isolation plates. These unwanted microbial taxa were removed by exposing the gut contents to polyvalent bacteriophages specifically targeting different background bacterial taxa and after their removal from the isolation plates previously undetected and novel actinomycetes were successfully cultured from the gut samples. CONCLUSIONS: Use of bacteriophages as a means of selective pressure successfully revealed the presence of novel actinomycete species within the guts of C. lacteus. SIGNIFICANCE AND IMPACT OF THE STUDY: Molecular ecology has undoubtedly revealed the fascinating diversity of micro-organisms, which cannot be cultured. However, these advances in the field still have not provided the ability to detect and isolate micro-organisms effectively from their ecological niches. Accordingly, studies like the one described here have importance in increasing the chances of uncultured taxa to be isolated to complement molecular microbial ecological efforts towards the establishment of an understanding on the diversity of termite gut microflora.     

Trend,signal and noise in the ecology of Ostracoda: information from rare species in low-diversity assemblages

Samples of Ostracoda from nearshore marine environments, where the water is more likely to be brackish or hypersaline, typically have low species diversity and are dominated by such species as Cyprideis torosa. In high-diversity samples from normal-marine environments, rare species are likely to contribute to environmental noise. Evaluation of low-diversity samples from Lake Manzala, Egypt, however, shows that the environmental signal provided by rare species can be masked by the overwhelmingly dominant species, C. torosa. In such instances, the dominant species should be removed from the data set and studies based on a large sample of the rare species.     

Bacterial composition of sponges,sediment and seawater in enclosed and open marine lakes in Ha Long Bay Vietnam

ABSTRACT

Marine lakes are landlocked bodies of seawater, isolated to varying degrees from the surrounding marine habitat. Isolated lakes generally have lower pH values, salinities and higher temperatures than more open lakes. We used a 16S rRNA gene barcoded pyrosequencing approach to study the bacterial communities of two sponge species, sediment and seawater in one enclosed and two open marine lakes. Bacterial communities of the sponge Spheciospongia solida mainly consisted of Proteobacteria, Cyanobacteria and Bacteroidetes. In contrast, Proteobacteria, Chloroflexi and Acidobacteria dominated the bacterial communities of the sponge Spongia ceylonensis. Although only a limited amount of samples were collected, both water and S. ceylonensis sponge had higher relative abundances of Cyanobacteria in the enclosed lake, which mainly consisted of OTUs assigned to the genus Synechococcus. This is in line with a number of previous studies, which have shown that environmental conditions found within low pH environments such as marine lakes benefit the growth of Synechococcus spp. Future studies should address the mechanism by which Synechococcus spp. may help host sponges and their bacterial communities adapt to low pH conditions in isolated marine lakes and other low-pH environments.     

Culturing marine bacteria – an essential prerequisite for biodiscovery

The potential for using marine microbes for biodiscovery is severely limited by the lack of laboratory cultures. It is a long-standing observation that standard microbiological techniques only isolate a very small proportion of the wide diversity of microbes that are known in natural environments from DNA sequences. A number of explanations are reviewed. The process of establishing laboratory cultures may destroy any cell-to-cell communication that occurs between organisms in the natural environment and that are vital for growth. Bacteria probably grow as consortia in the sea and reliance on other bacteria for essential nutrients and substrates is not possible with standard microbiological approaches. Such interactions should be considered when designing programmes for the isolation of marine microbes. The benefits of novel technologies for manipulating cells are reviewed, including single cell encapsulation in gel micro-droplets. Although novel technologies offer benefits for bringing previously uncultured microbes into laboratory culture, many useful bacteria can still be isolated using variations of plating techniques. Results are summarized for a study to culture bacteria from a long-term observatory station in the English Channel. Bacterial biodiversity in this assemblage has recently been characterized using high-throughput sequencing techniques. Although Alphaproteobacteria dominated the natural bacterial assemblage throughout the year, Gammaproteobacteria were the most frequent group isolated by plating techniques. The use of different gelling agents and the addition of ammonium to seawater-based agar did lead to the isolation of a higher proportion of Alphaproteobacteria. Variation in medium composition was also able to increase the recovery of other groups of particular interest for biodiscovery, such as Actinobacteria.     

Immunofluorescence detection of the denitrifying strain Pseudomonas stutzeri (ATCC 14405) in seawater and intertidal sediment environments

A strain-specific immunofluorescence assay for enumeration of a marine denitrifying bacterium was developed and applied in the marine environment. The polyclonal antiserum for Pseudomonas stutzeri (ATCC 14405) did not react with other pseudomonads, other heterotrophs, or autotrophic nitrifying strains. The abundance of P. stutzeri in the shallow water column of Monterey Bay was less than 0.1% of the total bacterial abundance and decreased with depth, whereas the total bacterial abundance was variable and nearly constant with depth. P. stutzeri was also detected in the sediments of a microbial mat from Tomales Bay. The relatively low contribution of P. stutzeri to the total bacterial abundance in both environments implies that it is not a major component of the heterotrophic assemblage. This conclusion appears to hold for most other strains for which specific assays have been applied in the marine environment. The isolation of several different denitrifying strains from local marine environments implies that the culturable population is quite diverse, even in the absence of different selective enrichment media. Thus, strain specific immunofluorescence is of limited use in quantifying functional groups of bacteria. Conversely, they provide specific information on the diversity of natural populations and their relation to culturable strains.Offprint requests to: B. Ward     

Marine yeasts as biocontrol agents and producers of bio-products

As some species of marine yeasts can colonize intestine of marine animals, they can be used as probiotics. It has been reported that β-glucans from marine yeast cells can be utilized as immuno-stimulants in marine animals. Some siderophores or killer toxins produced by marine yeasts have ability to inhibit growth of pathogenic bacteria or kill pathogenic yeasts in marine animals. The virulent factors from marine pathogens can be genetically displayed on marine yeast cells, and the yeast cells displaying the virulent factors can stimulate marine animals to produce specific antibody against the pathogens. Some marine yeast cells are rich in proteins and essential amino acids and can be used in nutrition for marine animals. The marine yeast cells rich in lipid can be used for biodiesel production. Recently, it has been reported that some strains of Yarrowia lipolytica isolated from marine environments can produce nanoparticles. Because many marine yeasts can remove organic pollutants and heavy metals, they can be applied to remediation of marine environments. It has been shown that the enzymes produced by some marine yeasts have many unique properties and many potential applications.     

Phylogenetic relationships and taxonomic position of Chlorella -like isolates from low pH environments (pH < 3.0)

Background  

Little is known about phytoplankton communities inhabiting low pH environments such as volcanic and geothermal sites or acidic waters. Only specialised organisms are able to tolerate such extreme conditions. There is, thus, low species diversity. We have characterised the previously isolated acid tolerant Chlorella -like microalgae Viridiella fridericiana and Chlorella protothecoides var. acidicola by microscopical and biomolecular methods in order to assess their phylogenetic relationships.     

Identification of Bacterial Strains Isolated from the Mediterranean Sea Exhibiting Different Abilities of Biofilm Formation

The Mediterranean Sea has rarely been investigated for the characterization of marine bacteria as compared to other marine environments such as the Atlantic or Pacific Ocean. Bacteria recovered from inert surfaces are poorly studied in these environments, when it has been shown that the community structure of attached bacteria can be dissimilar from that of planktonic bacteria present in the water column. The objectives of this study were to identify and characterize marine bacteria isolated from biofilms developed on inert surfaces immersed in the Mediterranean Sea and to evaluate their capacity to form a biofilm in vitro. Here, 13 marine bacterial strains have been isolated from different supports immersed in seawater in the Bay of Toulon (France). Phylogenetic analysis and different biological and physico-chemical properties have been investigated. Among the 13 strains recovered, 8 different genera and 12 different species were identified including 2 isolates of a novel bacterial species that we named Persicivirga mediterranea and whose genus had never been isolated from the Mediterranean Sea. Shewanella sp. and Pseudoalteromonas sp. were the most preponderant genera recovered in our conditions. The phenotypical characterization revealed that one isolate belonging to the Polaribacter genus differed from all the other ones by its hydrophobic properties and poor ability to form biofilms in vitro. Identifying and characterizing species isolated from seawater including from Mediterranean ecosystems could be helpful for example, to understand some aspects of bacterial biodiversity and to further study the mechanisms of biofilm (and biofouling) development in conditions approaching those of the marine environment.     

Unique Actinomycetes from Marine Caves and Coral Reef Sediments Provide Novel PKS and NRPS Biosynthetic Gene Clusters

In the ever-expanding search for novel bioactive molecules and enzymes, marine actinomycetes have proven to be a productive source. While open reef sediment and sponge-associated actinomycetes have been extensively examined, their marine cave counterparts remain unevaluated. Anchialine cave systems in the Bahamas offered an ideal setting to evaluate the occurrence and variation within sediment-associated actinomycete communities. While in close geographical proximity to open reef environments, these systems provide a specialized environmental niche devoid of light and direct exposure to nutrient input. In the present study, selective isolation techniques and molecular methods were used to test the hypothesis that variable distribution of actinomycetes and secondary metabolite gene clusters occur between open reef and marine cave systems. The results indicated that differences exist within the culturable sediment-associated actinomycete communities between marine caves and open reef systems, with members of the genus Streptomyces dominating cultures from open reef sediments and a more diverse suite of actinomycetes isolated from marine cave sediment samples. Within the cave isolates, members of the proposed genus Solwaraspora were the most represented. Based on PKS- and NRPS-gene-targeted PCR amplification and sequencing, geographic variation in the occurrence of these biosynthetic pathways was also observed. These findings indicate that marine cave systems are a lucrative source in the search for novel secondary metabolite producers with biotechnological applications and that environmental and geographic factors likely affect the occurrence of these biosynthetic pathways.