Huajun Zhang

Effect of Oxidative Stress Induced by Brevibacterium sp BS01 on a HAB Causing Species-Alexandrium tamarense

Harmful algal blooms occur all over the world, destroying aquatic ecosystems and threatening other organisms. The culture supernatant of the marine algicidal actinomycete BS01 was able to lysis dinoflagellate Alexandrium tamarense ATGD98-006. Physiological and biochemical responses to oxidative stress in A. tamarense were investigated to elucidate the mechanism involved in BS01 inhibition of algal growth. Transmission electron microscope analysis revealed that there were some chloroplast abnormalities in response to BS01 supernatant. The decrease in cellular-soluble protein content suggested that cell growth was greatly inhibited at high concentration of BS01 supernatant. The increase in the levels of reactive oxygen species (ROS) and malondialdehyde contents following exposure to BS01 supernatant indicated that algal cells suffered from oxidative damage. The content of pigment was significantly decreased after 12 h treatment, which indicated that the accumulation of ROS destroyed pigment synthesis. Moreover, the decrease of Fv/Fm ratio suggested that in the photosynthetic system, the dominant sites producing ROS were destroyed by the supernatant of the BS01 culture. The activities of the antioxidant enzymes including superoxide dismutase and peroxidase increased in a short time and decreased slightly with increasing exposure time. A real-time PCR assay showed changes in the transcript abundances of two photosynthetic genes, psbA and psbD. The results showed that BS01 supernatant reduced the expression of the psbA gene after 2 h exposure, but the expression of the psbD gene was increased at concentrations of 1.0 and 1.5%. Our results demonstrated that the expression of the psbA gene was inhibited by the BS01 supernatant, which might block the electron transport chain, significantly enhancing ROS level and excess activity of the antioxidant system. The accumulation of ROS destoryed pigment synthesis and membrane integrity, and inhibited or ultimately killed the algal cells.

Tenacibaculum xiamenense sp nov, an algicidal bacterium isolated from coastal seawater

A Gram-stain-negative, elongated rod-shaped, yellow-pigmented, aerobic bacterial strain, designated WJ-1(T), was isolated from coastal seawater in Xiamen, Fujian province, China. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain WJ-1(T) fell within the genus Tenacibaculum and was most closely associated with Tenacibaculum aestuarii SMK-4(T) (96.7% 16S rRNA gene sequence similarity); lower similarities were shown to other members of the genus Tenacibaculum (<96.2%). The strain formed a distinct lineage with Tenacibaculum litopenaei B-I(T) (96.0%), Tenacibaculum geojense YCS-6(T) (94.5%) and Tenacibaculum jejuense CNURIC 013(T) (95.4%). Growth was observed at temperatures from 16 to 38 °C, at salinities from 2 to 4% and at pH 6-9. The major fatty acids were summed feature 3 (C(16:1)ω6c and/or C(16 1)ω7c), iso-C(17:0) 3-OH, iso-C(15:0) and iso-C(15:0) 3-OH. The DNA G+C content of strain WJ-1(T) was 33.2 mol% and the major respiratory quinone was menaquinone-6 (MK-6). Differential phenotypic properties and phylogenetic distinctiveness in this study distinguished strain WJ-1(T) from all other members of the genus Tenacibaculum. According to the morphology, physiology, fatty acid composition and 16S rRNA gene sequence data, strain WJ-1(T) represents a novel species of the genus Tenacibaculum, for which the name Tenacibaculum xiamenense sp. nov. is proposed. The type strain is WJ-1(T) ( =CGMCC 1.12378(T) =LMG 27422(T)).

Mangrovimonas yunxiaonensis gen nov, sp nov, isolated from mangrove sediment

A Gram-negative, short-rod-shaped, orange-pigmented bacterium, strain LYYY01(T), was isolated from a mangrove sediment sample collected from Yunxiao mangrove National Nature Reserve, Fujian Province, China. 16S rRNA gene sequence comparisons showed that strain LYYY01(T) is a member of the family Flavobacteriaceae, forming a distinct lineage with species of the genera Meridianimaribacter, Sediminibacter, Gelidibacter and Subsaximicrobium. The 16S rRNA gene sequence similarity between strain LYYY01(T) and the type strains of related species ranged from 93.9 to 90.9%. Growth was observed at temperatures from 10 to 38 °C, at salinities from 1 to 7% and at pH from 6 to 10. The DNA G+C content of the strain was 38.6 mol% and the major respiratory quinone was menaquinone-6 (MK-6). The major fatty acids were iso-C15:1 (27.6%), iso-C15:0 (24.0%), iso-C17:0 3-OH (12.0%) and iso-C16:0 3-OH (6.2%). According to its morphology, physiology, fatty acid composition and 16S rRNA gene sequence data, strain LYYY01(T) is considered to represent a novel species of a new genus in the family Flavobacteriaceae, for which the name Mangrovimonas yunxiaonensis gen. nov., sp. nov. is proposed. The type strain of Mangrovimonas yunxiaonensis is LYYY01(T) (=CGMCC 1.12280(T)=LMG 27142(T)).

First Report of Pseudobodo sp, a New Pathogen for a Potential Energy-Producing Algae: Chlorella vulgaris Cultures

Chlorella vulgaris, is a kind of single-celled green algae, which could serve as a potential source of food and energy because of its photosynthetic efficiency. In our study, a pathogenic organism targeting C. vulgaris was discovered. The algae-lytic activity relates to a fraction from lysates of infected C. vulgaris that was blocked upon filtration through a 3 µm filter. 18S rRNA gene sequence analysis revealed that it shared 99.0% homology with the protist Pseudobodo tremulans. Scanning electron microscope analysis showed that Pseudobodo sp. KD51 cells were approximately 4–5 µm long, biflagellate with an anterior collar around the anterior part of the cell in unstressed feeding cells. Besides the initial host, Pseudobodo sp. KD51 could also kill other algae, indicating its relatively wide predatory spectrum. Heat stability, pH and salinity tolerance experiments were conducted to understand their effects on its predatory activities, and the results showed that Pseudobodo sp. KD51 was heat-sensitive, and pH and salinity tolerant.

Mameliella phaeodactyli sp. nov., a member of the family Rhodobacteraceae isolated from the marine algae Phaeodactylum tricornutum

A novel Gram-staining-negative, aerobic, rod-shaped, non-motile, yellow bacterium designated strain KD53(T), was isolated from a culture of the alga Phaeodactylum tricornutum from Xiamen, Fujian Province, China. 16S rRNA gene sequence comparison showed that strain KD53(T) was a member of the Roseobacter clade within the family Rhodobacteraceae , forming a distinct lineage with species of the genus Mameliella . The 16S rRNA gene sequence similarities between strain KD53(T) and other strains examined were all less than 97.0%. Strain KD53(T) was found to grow optimally at 28 °C, at pH 7.5-8.0 and in the presence of 3% (w/v) NaCl. The dominant fatty acids of strain KD53(T) were C18 : 1ω6c and/or C18 : 1ω7c, C18 : 0 and C16 : 0. The major polar lipids were phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol. The DNA G+C content was 65 mol% and the major respiratory quinone was ubiquinone 10 (Q-10). On the basis of phenotypic data and phylogenetic inference, strain KD53(T) represents a novel member of the genus Mameliella , then the name Mameliella phaeodactyli sp. nov. is proposed. The type strain is KD53(T) ( =MCCC 1K00273(T) =KCTC 42178(T)).

Erythrobacter luteus sp. nov., isolated from mangrove sediment.

A Gram-staining-negative, orange-pigmented, aerobic bacterial strain, designated KA37T, was isolated from a mangrove sediment sample collected from Yunxiao mangrove National Nature Reserve, Fujian Province, China. Growth was observed at 4-37 °C, 0-3% (w/v) NaCl and pH 5-10. Mg2+ ions were required for growth. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that the isolate was a member of the genus Erythrobacter, which belongs to the family Erythrobacteraceae. Strain KA37T was most closely related to Erythrobacter gangjinensis KCTC 22330T (96.9% sequence similarity), followed by Erythrobacter marinus KCTC 23554T (96.8%); similarity to other members of the genus was below 96.6%. The major fatty acids were C17 : 1ω6c, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). Strain KA37T did not produce bacteriochlorophyll a. The predominant respiratory quinone was ubiquinone 10 (Q-10). The polar lipids of strain KA37T were sphingoglycolipid, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, five unknown lipids and one unidentified phospholipid. According to its morphology, physiology, fatty acid composition and 16S rRNA sequence, the novel strain most appropriately belongs to the genus Erythrobacter, but can be distinguished readily from species of the genus Erythrobacter with validly published names. The name Erythrobacter luteus sp. nov. is proposed, with strain KA37T ( = MCCC 1F01227T = KCTC 42179T) as the type strain.

Chitinimonas prasina sp. nov., isolated from lake water.

A Gram-stain-negative, elongated rod-shaped, motile by gliding, green-pigmented, aerobic bacterial strain, designated LY03(T), was isolated from lake water in Xiamen, Fujian Province, China. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that the isolate was a member of the genus Chitinimonas, which belongs to the family Burkholderiaceae. Strain LY03(T) was most closely related to Chitinimonas taiwanensis LMG 22011(T) (96.02 % 16S rRNA gene sequence similarity), followed by Chitinimonas koreensis KACC 11467(T) (94.85 %), and the three strains formed a distinct lineage from other strains in the phylogenetic analyses. Optimum conditions for growth were 37 °C, pH 7-9 and without NaCl. The major fatty acids were summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c), C16 : 0 and C10 : 0 3-OH. The DNA G+C content of strain LY03(T) was 63.6 mol% and the major respiratory quinone was ubiquinone-8 (Q-8). The polar lipids were found to consist of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unknown polar lipids and unidentified phospholipids. Differential phenotypic properties and phylogenetic distinctiveness distinguished strain LY03(T) from all other members of the genus Chitinimonas. On the basis of its morphology, physiology, fatty acid composition and 16S rRNA gene sequence data, strain LY03(T) represents a novel species of the genus Chitinimonas, for which the name Chitinimonas prasina sp. nov. is proposed. The type strain is LY03(T) ( = MCCC 1F01209(T) = KCTC 32574(T)).

Influence of plaque-forming bacterium, Rhodobacteraceae sp: On the growth of Chlorella vulgaris

Experiments were conducted to find out the molecular features, infection process of a special alga plaque-forming microorganism and its potential influence on the biomass of Chlorella vulgaris during the infection process. Direct contact between the algal cell and the bacterium may be the primary steps needed for the bacterium to lyse the alga. Addition of C. vulgaris cells into f/2 medium allowed us obtain the object bacterium. The 16S rRNA gene sequence comparisons results showed that the plaque-forming bacterium kept the closest relationship with Labrenzia aggregata IAM 12614(T) at 98.90%. The existence of the bacterium could influence both the dry weight and lipid content of C. vulgaris. This study demonstrated that direct cell wall disruption of C. vulgaris by the bacterium would be a potentially effective method to utilize the biomass of microalgae.

Whole-Genome Sequence of Marine Bacterium Phaeodactylibacter xiamenensis Strain KD52, Isolated from the Phycosphere of Microalga Phacodactylum tricornutum

ABSTRACT Phaeodactylibacter xiamenensis KD52 is a novel bacterium isolated from a culture of the alga Phaeodactylum tricornutum in Xiamen, Fujian Province, China. Here, we present the first draft genome sequence of this strain, which will provide an opportunity to further understand the functional genes related to signing for nutrition from the host algae and the molecular mechanisms underlying its beneficial properties.

Cyclobacterium xiamenense sp nov, isolated from aggregates of Chlorella autotrophica, and emended description of the genus Cyclobacterium

A novel Gram-stain-negative, horseshoe-shaped, non-motile bacterium, designated strain KD51(T), forming colonies coloured pink by carotenoid pigments, was isolated from aggregates of the alga Chlorella autotrophica collected from the coastal sea off the city of Xiamen, Fujian Province, China. 16S rRNA gene sequence comparison showed that strain KD51(T) was a member of the genus Cyclobacterium, forming a distinct lineage with Cyclobacterium lianum HY9(T). The 16S rRNA gene sequence similarity between strain KD51(T) and the type strains of species of the genus Cyclobacterium ranged from 92.1 % to 95.2 %. Growth occurred at 4-40 °C (optimum, 28 °C), in the presence of 3-9 % NaCl (optimum, 3-5 %) and at pH 6-10 (optimum, pH 7.5). The dominant fatty acids (>20 %) of strain KD51(T) were iso-C15 : 0 (32.2 %) and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c; 22.2 %). The DNA G+C content was 41.7 mol% and the only respiratory quinone was menaquinone-7. On the basis of phenotypic data and phylogenetic inference, strain KD51(T) represents a novel species of the genus Cyclobacterium, for which the name Cyclobacterium xiamenense sp. nov. is proposed. The type strain is KD51(T) ( = CGMCC 1.12432(T) = KCTC 32253(T)). An emended description of the genus Cyclobacterium is also proposed.