ALBERT

Description: It is well recognized that microorganisms associated with marine invertebrates, in particular sponges and hard corals, are an excellent source of new natural products. Therefore, the diversity of bacteria associated with marine invertebrates and their potential to produce bioactive compounds have received much attention in recent years. We report here for the first time on the biodiversity of bacteria associated with the soft coral Alcyonium digitatum, which is abundant in the Baltic Sea. In order to increase the cultured diversity, bacteria were isolated using four different media, identified with support of 16S rRNA gene sequences and screened for antimicrobial activity using two different media. Activity of crude extracts was tested against Bacillus subtilis, Staphylococcus epidermidis, Escherichia coli, and the yeast Candida albicans. A total of 251 coral-associated bacterial isolates were classified and found to belong to 41 species in 14 genera of the Firmicutes, Actinobacteria, Gammaproteobacteria, and Alphaproteobacteria. The genus Bacillus was most abundant and diverse with 17 recognized species. Forty-eight percent of all 251 isolates exhibited antimicrobial activity. All isolates of Bacillus methylotrophicus and Bacillus amyloliquefaciens displayed inhibition of at least three out of the four tested microorganisms. It became obvious during this study that the production of antibiotic substances not only is strain-specific, but in many cases also depends on the media composition and growth conditions. In addition, the antimicrobial potential of bacteria associated with A. digitatum may represent a promising source for antimicrobial substances.

Description: Beschreibung:Discovery of novel natural products from soft corals were reported with many achievement so far. Soft coral associated bacteria have gained interest for several reasons such as for marine environmental protection and bio-mining of natural products from microorganism as compared to the animals. This work focused on communities of soft coral associated bacteria and on the search for new antimicrobial substances and new natural products as potential candidates for new drugs. Thus, soft coral associated bacteria were quite abundant and good sources of antimicrobial producers. The results from cultivation-based studies and sequence analysis of 16S rRNA genes of bacterial communities associated with the soft coral A. digitatum are reported in this study. A total of 251 isolates were identified as belonging to 4 phyla Firmicutes, Actinobacteria, Gammaproteobacteria, and Alphaproteobacteria. Four of these isolates may be new species, 2 isolates of Firmicutes, 1 Gammaproteobacterium and 1 Alphaproteobacterium. The high diversity of the bacterial communities and their antimicrobial activities suggest the contribution of the associated bacteria to the coral health. The results from antimicrobial tests demonstrated that A. digitatum was the source of various bacteria producing antimicrobial substances. Antimicrobial activity of the isolates were found only in BM medium (3%), only in GYM medium (2%) or in both of these media (44%). Quite significant, all isolates belonging to the two species B. amyloliquefaciens and B. methylotrophicus showed antimicrobial activities. Some strains of the two species inhibited all four test microorganisms. Chemical analyis revealed that the two Bacillus sp. strains produced various known cyclic peptides as well as presumably new metabolites. They represented highly potent producers of antimicrobials. All isolates of Actinobacteria produced antimicrobial substances, that inhibited particulary Gram-positive bacteria. In addition to a marine Micrococcus isolate, three isolates of Firmicutes were thoroughly studied in regard to analysis of production of new compounds. In addition a number of known compounds were identified, including several peptides. The metabolites of the four strains were examined and purified by using several HPLC systems. The biological activities of pure compounds were studied using antibacterial, antifungal, cytotoxic, and enzyme assays. Eleven compounds were purified and applied to bioassays. One of the proposed known cyclic peptides showed antimicrobial activity against both B. subtilis and E. coli, whereas the others showed inhibition of methicillin-resistant Staphylococcus aureus (MRSA) and phosphodiesterase 4β2. One of compounds, which were considered as new compounds, inhibited fungus Trichophyton rubrum and enzyme phosphodiesterase 4β2. The structure elucidations of all pure compounds are in progress.  

Description: Soft coral is marine organism considered as a source of bioactive compounds. However, the relationship between soft coral, its associated microorganisms and its bioactive compounds are still discussed. Four among five collected specimens of soft coral were identified as Sinularia gibberosa Tixier-Durivault, 1970 (code: SH1); Sinularia maxima Verseveldt, 1971 (code: SH2); Sinularira capillosa Tixier-Durivault, 1970 (code: SH3); and Sinularia mira Tixier-Durivault, 1970 (code: SH4). 28 bacteria strains were isolated from specimens of soft corals by traditional culture method, including 26 strains of Firmicutes phylum and two others of Proteobacteria phylum. Among 25 strains tested for antibiotic activity, only the KH4 exhibited resistance to Cefazoline, then this strain was identified as Bacillus cereus 1 by using the API 50CHB KIT with accuracy of 99.7%. The other strains showed the sensitivity to Cefazolin with inhibitable zone ranging from 6 to 17mm. Strains of KH6 and KH10 showed the weak sensitivity with Gentamicine and Cefazolin, while KH18 showed the weak sensitivity to Tetracyline.

Description: Published

Description: El Niño and the prolonged warm sea surface temperature significantly impacted coral reefs and caused coral bleaching in some parts of the world. This study evaluated the density of symbiotic algae and bacteria associated with the three coral species, namely Acropora hyacinthus, Acropora muricata, and Acropora robusta, collected in Hang Rai, Ninh Thuan in May, June, August 2016, and June 2017. The number of zooxanthellae with each coral species was statistically significant and correlated with several environmental factors, suggesting that symbiotic algae could play a key role in coral health. The number of associated microbial with the three coral species was significantly different; they tended to depend on sampling time rather than coral species-specific. At the time of ENSO (2016), the difference in the total associated bacteria with all three coral species was statistically significant. While the total number of related bacteria with all three species of coral collected in 2017 did not differ from the total of bacteria in ambient water. In conclusion, symbiotic algae tend to be species-specific, whereas bacteria fluctuate significantly over sampling time. Studying the molecular issues of microalgae, the presence, the role of some groups of bacteria involved in the N, C, P, and S cycles, and the influence of environmental parameters should also be encouraged to understand the relationship of coral holobiont better.

Description: Published

Description: Refereed

Description: The marine actinomyces Micrococcus was the most common bacterium among the isolates corals, sponges, and alga isolates. Only a few investigations of natural compounds from Micrococcus sp. were reported previously. This study implicated the soft coral-associated Micrococcus sp. strain A-2-28 (following relative Micrococcus flavus LW4T) for large-scale cultivation, chemical analyses, and biological activities. Whereas crude extract of the strain A-2-28 inhibited only Staphylococcus epidermidis, metabolites profiles and pure compounds from strain A-2-28 showed that this strain produced phytohormone (IAA), metabolized some new compounds which were almost inactive for biological tests. This work suggested that it is possible to plan a new strategy for improving coral health and resilience though their associated microbial.

Description: Published

Description: Refereed