Bacterial community structure analysis of deep-sea water and surface seawater in Japan by pyrosequencing

Until recent years, marine bacterial researches have been conducted mainly on surface seawater (SSW) and marine sediment, but only few studies have been undertaken on deep-sea water (DSW). Therefore, in this study, bacterial community structures of DSW and SSW collected from seven DSW pumping stations in Japan were investigated by molecular biological techniques using a 454 FLX sequencer. The result of pyrosequencing analysis showed that the bacterial diversity of DSW was considerably higher than that of SSW as we studied before. The proportions of several phyla (Actinobacteria, Chloroexi, Gemmatimonadetes, and SAR046) in DSW were higher than those in SSW. In addition, principal coordinates analysis (PCoA) based on the pyrosequencing data showed that DSW samples tended to form clusters separated from those of SSW samples. These results indicate that the bacterial community structure of DSW is dierent from that of SSW and there are various bacteria adapting in DSW environment, which differ from those in SSW. Therefore, DSW is believed to contain novel bacteria not found in SSW as a source for finding novel bioactive compounds

Development of an in vivo-mimic silkworm infection model with Mycobacterium avium complex

In vivo-mimic silkworm infection models with Mycobacterium avium and Mycobacterium intracellulare were newly established to evaluate the therapeutic effects of anti-M. avium complex (MAC) antibiotics. Silkworms raised at 37°C died within 72 hours of an injection of M. avium or M.intracellulare (2.5 × 107 colony-forming unit (CFU)/larva·g) into the hemolymph. Clinical anti-mycobacterial (tuberculosis) antibiotics were evaluated under these conditions. Clarithromycin, kanamycin, streptomycin, amikacin, and ciprofloxacin exerted therapeutic effects in a dose-dependent manner, which was consistent with those in the mouse model. Furthermore, three effective actinomycete culture broths were selected in the screening program of our microbial broth library using the silkworm model, and four active metabolites, ohmyungsamycins A and B (1 and 2), chartreusin (3), and griseoviridin (4), were identified. Among these compounds, 1 showed the lowest 50% effective dose (ED50) value (8.5 µg/larva·g), while 3 had the best ED50/minimum inhibitory concentration (MIC) ratio (7.4). These results indicate that silkworm models are a useful tool for identifying anti-MAC antibiotics candidates with veritable therapeutic effects

Nomimicins B–D, new tetronate-class polyketides from amarine-derived actinomycete of the genus Actinomadura

Three new tetronate-class polyketides, nomimicins B, C, and D, along with nomimicin, hereafter named nomimicin A, were isolated from the culture extract of Actinomadura sp. AKA43 collected from floating particles in the deep-sea water of Sagami Bay, Japan. The structures of nomimicins B, C, and D were elucidated through the interpretation of NMR and MS analytical data, and the absolute configuration was determined by combination of NOESY/ROESY and ECD analyses. Nomimicins B, C, and D showed antimicrobial activity against Gram-positive bacteria, Kocuria rhizophila and Bacillus subtilis, with MIC values in the range of 6.5 to 12.5 μg/mL. Nomimicins B and C also displayed cytotoxicity against P388 murine leukemia cells with IC(50) values of 33 and 89 μM, respectively

Antibacterial Activity against Clinical Isolates and In Vivo Efficacy of Coralmycins

Coralmycins, such as coralmycin A and DH-coralmycin A, have novel molecular skeletons and have been reported to exhibit potent antibacterial activity against standard Gram-positive bacterial strains. Here, the in vitro antibacterial activity against an extensive clinical isolate collection, time-kill kinetics, pharmacokinetics (PK), and in vivo efficacy of coralmycins were studied. Coralmycin A showed potent antibacterial activity with an MIC90 of 1 mg/L against 73 clinical methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci isolates, which was 2–8 times higher than the corresponding activities of DH-coralmycin A, vancomycin, daptomycin, and linezolid, and against 73 vancomycin-resistant Enterococcus and Streptococcus pneumoniae isolates, which was 4–16 times higher than the corresponding activities of DH-coralmycin A, daptomycin, and linezolid. Pharmacokinetic analysis after i.v. injection showed that coralmycins have a moderate volume of distribution and moderate-to-high clearance in mice. The coralmycin A and DH-coralmycin A bioavailability values were 61.3% and 11.7%, respectively, after s.c. administration. In a mouse respiratory tract infection model, coralmycin A showed bacteriostatic and bactericidal in vivo efficacies at an s.c. administration of 4 and 100 mg/kg bid, respectively; these efficacies were similar to those of vancomycin at 4 and 20 mg/kg bid, respectively. The present findings indicate that coralmycin A has great potential as a new class of antibiotic for treating infections caused by multidrug-resistant Gram-positive bacteria

Nomimicins B–D, new tetronate-class polyketides from amarine-derived actinomycete of the genus Actinomadura

Three new tetronate-class polyketides, nomimicins B, C, and D, along with nomimicin, hereafter named nomimicin A, were isolat-ed from the culture extract of Actinomadura sp. AKA43 collected from floating particles in the deep-sea water of Sagami Bay,Japan. The structures of nomimicins B, C, and D were elucidated through the interpretation of NMR and MS analytical data, andthe absolute configuration was determined by combination of NOESY/ROESY and ECD analyses. Nomimicins B, C, and Dshowed antimicrobial activity against Gram-positive bacteria, Kocuria rhizophila and Bacillus subtilis, with MIC values in therange of 6.5 to 12.5 μg/mL. Nomimicins B and C also displayed cytotoxicity against P388 murine leukemia cells with IC50 valuesof 33 and 89 μM, respectively