Three New Diketopiperazines from the Previously Uncultivable Marine Bacterium Gallaecimonas mangrovi HK-28 Cultivated by iChip.

The in situ application of iChip cultivation in mangrove sediment from Hainan province, China, led to the isolation of a novel bacterial species Gallaecimonas mangrovi HK-28. The extract of G. mangrovi HK-28 exhibited antibiotic activity against the aquatic pathogen Vibrio harveyi, and its chemical constituents were further investigated by bioactivity-guided isolation. Three new diketopiperazines, gallaecimonamides A-C, were accordingly isolated from the AcOEt extract of the fermentation broth of G. mangrovi HK-28. The planar structures of gallaecimonamides A-C were determined using HR-ESI-MS together with 1D- and 2D-NMR. The absolute configurations of gallaecimonamides A-C were assigned by optical rotation, NOESY experiment and TDDFT ECD calculations. The in vitro antibacterial and antimalarial activities of gallaecimonamides A-C were assessed. Gallaecimonamide A was found to display antibacterial activity against V. harveyi with a MIC value of 50 µm. However, gallaecimonamides B and C showed no antibacterial activity against V. harveyi (MIC >300 µm). In addition, all the isolates did not exhibit any inhibitory activities against V. parahaemolyticus (MIC>300 µm) and Plasmodium falciparum W2 (EC50 >100 µg/mL).

Pararhodobacter marinus sp. nov., a bacterium isolated from marine sediment in the East China Sea and emended description of the genus Pararhodobacter.

A Gram-negative, rod-shaped, non-motile and strictly aerobic bacterium, designated ZQ420T, was isolated from marine sediment sampled on Zhoushan Island located in the East China Sea. Strain ZQ420T was able to grow at 10-45 °C, 0-12.0 % (w/v) NaCl and pH 5.5-9.0. Catalase and oxidase activities, nitrate reduction, H2S production, hydrolysis of starch, casein, Tween 20, 40 and 80 were positive. Indole, methyl red, Voges-Proskauer test, hydrolysis of gelatin and Tween 60 were negative. The major cellular fatty acids were C18 : 1 ω7c, C16 : 0 and 11-methyl C18 : 1ω7c. Ubiquinone-10 (Q-10) was the only detected respiratory quinone. The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, three unidentified phospholipids, three unidentified glycolipids, two unidentified aminolipid and two unidentified lipids. The DNA G+C content was 64.8 mol%. According to 16S rRNA gene sequence similarities, strain ZQ420T shared 97.9, 96.3 and 96.3 % similarities to the following species with validated names Pararhodobacteraggregans D1-19T, Pseudo rhodobacter psychrotolerans PAMC27389T and Pseudo rhodobacter collinsensis 4-T-34T, respectively. While sharing lower sequence similarities (<96.0 %) to other type species. Phylogenetic analyses showed that strain ZQ420T and P. aggregans D1-19T formed an independent cluster in the phylogenetic trees. The average nucleotide identity value between strain ZQ420T and P. aggregans D1-19T was 79.1 %. The in silico DNA-DNA hybridization analysis revealed that strain ZQ420T shared 21.5 % DNA relatedness with P. aggregans D1-19T. On the basis of its phenotypic, chemotaxonomic and genotypic characteristics, strain ZQ420T is considered to represent a novel species in the genus Pararhodobacter, for which the name Pararhodobactermarinus sp. nov. is proposed. The type strain is ZQ420T (=KCTC 62579T=MCCC 1K03530T).

Saccharospirillum mangrovi sp. nov., a bacterium isolated from mangrove sediment.

A Gram-negative, spirilla, non-spore-forming, motile and strictly aerobic bacterium, designated HK-33T, was isolated from a mangrove sediment sample in Haikou city, Hainan Province, China. Strain HK-33T was able to grow at 10-45 °C (optimum 37 °C), 0.5-12.0 % (w/v) NaCl (2.0 %, w/v) and pH 5.5-8.5 (pH 7.0). The major cellular fatty acids were C16 : 0 and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). Ubiquinone-8 was the predominant respiratory quinone, and Q-9 was present in trace amounts. The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified phospholipids, two unidentified glycolipids, an unidentified aminophosphoglycolipid and two unidentified lipids. The DNA G+C content was 57.3 mol%. According to 16S rRNA gene sequences similarity, strain HK-33T shared 98.6 %, 96.4%, 95.7 and 94.9 % sequence similarities to the species Saccharospirillum correiae CPA1T, Saccharospirillum impatiens EL-105T, Saccharospirillum salsuginis YIM-Y25T and Saccharospirillum aestuarii IMCC 4453T, respectively. Phylogenetic analysis showed that strain HK-33T was clustered with S. correiae CPA1T, S. impatiens EL-105T, S. salsuginis YIM-Y25T and S. aestuarii IMCC 4453T. Results of DNA-DNA hybridization analysis revealed that strain HK-33T shared 36.3±1.7 % DNA relatedness with S. correiae CPA1T. On the basis of its phenotypic, chemotaxonomic and genotypic characteristics, strain HK-33T is considered to represent a novel species in the genus Saccharospirillum, for which the name Saccharospirillummangrovi sp. nov. is proposed. The type strain is HK-33T (=KCTC 62178T=MCCC 1K03440T).

Marine-derived Trichoderma Species as a Promising Source of Bioactive Secondary Metabolites.

Marine-derived fungi Trichoderma genus are serving as a valuable resource for structurally novel natural products encompassing a variety of chemical substances and diverse pharmacological applications. So far, about 78 metabolites have been structurally documented from the species of marine Trichoderma genus and a large proportion of these metabolites exhibited therapeutic properties with potential application in drug discovery. This mini-review focuses on the structures and bioactivities of these secondary metabolites from marine-derived Trichoderma species.

Gallaecimonas mangrovi sp. nov., a novel bacterium isolated from mangrove sediment.

A Gram-stain negative, rod-shaped, non-motile, strictly aerobic bacterium HK-28T was isolated from a mangrove sediment sample in Haikou city, Hainan Province, China. Strain HK-28T was able to grow at 10-45 °C (optimum 25-30 °C), pH 5.0-8.5 (optimum 6.0-7.0) and 0.5-12.0% (w/v) NaCl (optimum 1.0-3.0%, w/v). The major cellular fatty acids were C16:0, Summed Feature 8 (C18:1 ω7c and/or C18:1 ω6c), Summed Feature 3 (C16:1 ω7c and/or C16:1 ω6c), C17:0, C12:0 3-OH and C17:1ω8c. Ubiquinone-8 (Q-8) was the predominant respiratory quinone. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified aminophospholipids, four unidentified phospholipids, two unidentified glycolipid, an unidentified glycophospholipid, an unidentified aminolipid and an unidentified lipid. The DNA G+C content was 50.2 mol%. Accoroding to 16S rRNA gene sequence similarities, strain HK-28T shared 97.1 and 96.7% sequence similarities to the validly named species Gallaecimonas xiamenensis MCCC 1A01354T and Gallaecimonas pentaromativorans MCCC 1A06435T, respectively, and shared lower sequence similarities (< 92.0%) to all other genera. Phylogenetic analysis showed strain HK-28T was clustered with G. pentaromativorans MCCC 1A06435T and G. xiamenensis MCCC 1A01354T. Strain HK-28T showed low DNA-DNA relatedness with G. xiamenensis MCCC 1A01354T (28.3 ± 1.5%) and G. pentaromativorans MCCC 1A06435T (25.2 ± 2.4%). On the basis of phenotypic, chemotaxonomic and genotypic characteristics, strain HK-28T is considered to represent a novel species in the genus Gallaecimonas, for which the name Gallaecimonas mangrovi sp. nov. is proposed. The type strain is HK-28T (= KCTC 62177T = MCCC 1K03441).