Dynamic bacterial community response to Akashiwo sanguinea (Dinophyceae) bloom in indoor marine microcosms.

We investigated the dynamics of the bacterial composition and metabolic function within Akashiwo sanguinea bloom using a 100-L indoor microcosm and metagenomic next-generation sequencing. We found that the bacterial community was classified into three groups at 54% similarity. Group I was associated with "during the A. sanguinea bloom stage" and mainly consisted of Alphaproteobacteria, Flavobacteriia and Gammaproteobacteria. Meanwhile, groups II and III were associated with the "late bloom/decline stage to post-bloom stage" with decreased Flavobacteriia and Gammaproteobacteria in these stages. Upon the termination of the A. sanguinea bloom, the concentrations of inorganic nutrients (particularly PO43-, NH4+ and dissolved organic carbon) increased rapidly and then decreased. From the network analysis, we found that the A. sanguinea node is associated with certain bacteria. After the bloom, the specific increases in NH4+ and PO43- nodes are associated with other bacterial taxa. The changes in the functional groups of the bacterial community from chemoheterotrophy to nitrogen association metabolisms were consistent with the environmental impacts during and after A. sanguinea bloom. Consequently, certain bacterial communities and the environments dynamically changed during and after harmful algal blooms and a rapid turnover within the bacterial community and their function can respond to ecological interactions.

Extremophile extracts and enhancement techniques show promise for the development of a live vaccine against Flavobacterium columnare.

The effects of temperature, ionic strength, and new cryopreservatives derived from polar ice bacteria were investigated to help accelerate the development of economical, live attenuated vaccines for aquaculture. Extracts of the extremophile Gelidibacter algens functioned very well as part of a lyophilization cryoprotectant formulation in a 15-week storage trial. The bacterial extract and trehalose additives resulted in significantly higher colony counts of columnaris bacteria (Flavobacterium columnare) compared to nonfat milk or physiological saline at all time points measured. The bacterial extract combined with trehalose appeared to enhance the relative efficiency of recovery and growth potential of columnaris in flask culture compared to saline, nonfat milk, or trehalose-only controls. Pre-lyophilization temperature treatments significantly affected F. columnare survival following rehydration. A 30-min exposure at 0 degrees C resulted in a 10-fold increase in bacterial survival following rehydration compared to mid-range temperature treatments. The brief 30 and 35 degrees C pre-lyophilization exposures appeared to be detrimental to the rehydration survival of the bacteria. The survival of F. columnare through the lyophilization process was also strongly affected by changes in ionic strength of the bacterial suspension. Changes in rehydration constituents were also found to be important in promoting increased survival and growth. As the sodium chloride concentration increased, the viability of rehydrated F. columnare decreased.

Characterization of phosphobacteria isolated from eutrophic aquatic ecosystems.

Phosphobacteria are able to enhance phosphorus availability in soil and improve crop yields. To develop such biofertilizers, 14 predominant phosphobacteria were isolated from eutrophic aquatic ecosystems. Molecular identification and phylogenetic analysis revealed three groups among the nine isolates of inorganic phosphate-solubilizing bacteria (IPSB): IPSB1 and IPSB2 belonged to the actinobacteria and flavobacteria, respectively, and the other seven belonged to the gamma-proteobacteria. Among five isolates of organic phosphorus-mineralizing bacteria (OPMB), two groups were present: OPMB1 and OPMB3 belonged to the beta-proteobacteria, while the other three belonged to the gamma-proteobacteria. The IPSB isolates released 62.8-66.7 mg P 1(-1) from tricalcium phosphate under shaking conditions, and 26.8 to 43.7 mg P 1(-1) under static conditions; the OPMB strains released 23.5-30.2 mg P 1(-1) from lecithin under shaking conditions, and 16.7-27.6 mg P 1(-1) under static conditions. To the best of our knowledge, this is the first report indicating that IPSBI (designated Aureobacterium resistents) as a tricalcium phosphate-solubilizing bacterium and OPMB1 and OPMB3 (designated Acidovorax temperans and Achromobacter xylosoxidans, respectively) are lecithin-mineralizing bacteria. This investigation demonstrated that a eutrophic aquatic ecosystem is a selective source of phosphobacteria and the screened phosphobacteria are a potential alternative to the development of biofertilizers.

A novel crude oil emulsifier excreted in the culture supernatant of a marine bacterium, Myroides sp. strain SM1.

A marine bacterium, Myroides sp. SM1, can grow on weathered crude oil and show emulsification of it. The biosurfactant able to emulsify crude oil was excreted in culture supernatant of Myroides sp. SM1 grown on marine broth, which was extracted with chloroform/methanol (1:1) at pH 7 and purified by normal and reverse phase silica gel column chromatographies. The compound was ninhydrin-positive, and the chemical structure was elucidated by nuclear magnetic resonance (NMR), infrared spectroscopy (IR), fast atom bombardment mass spectrometry, and gas chromatography-mass spectrometry (GC-MS) to be a mixture of L: -ornithine lipids, which were composed of L: -ornithine and a different couple of iso-3-hydroxyfatty acid (C(15)-C(17)) and iso-fatty acid (C(15) or C(16)) in a ratio of 1:1:1. The critical micelle concentration for a mixture of ornithine lipids was measured to be approximately 40 mg/l. A mixture of ornithine lipids exhibited emulsifying activity for crude oil in a broad range of pH, temperature, and salinity and showed higher surface activity for oil displacement test than other several artificial surfactants and a biosurfactant, surfactin.

Iron uptake mechanisms in the fish pathogen Tenacibaculum maritimum.

We present here the first evidence of the presence of iron uptake mechanisms in the bacterial fish pathogen Tenacibaculum maritimum. Representative strains of this species, with different serotypes and origins, were examined. All of them were able to grow in the presence of the chelating agent ethylenediamine-di-(o-hydroxyphenyl acetic acid) (EDDHA) and also produced siderophores. Cross-feeding assays suggest that the siderophores produced are closely related. In addition, all T. maritimum strains utilized transferrin, hemin, hemoglobin, and ferric ammonic citrate as iron sources when added to iron-deficient media. Whole cells of all T. maritimum strains, grown under iron-supplemented or iron-restricted conditions, were able to bind hemin, indicating the existence of constitutive binding components located at the T. maritimum cell surface. This was confirmed by the observation that isolated total and outer membrane proteins from all of the strains, regardless of the iron levels of the media, were able to bind hemin, with the outer membranes showing the strongest binding. Proteinase K treatment of whole cells did not affect the hemin binding, indicating that, in addition to proteins, some protease-resistant components could also bind hemin. At least three outer membrane proteins were induced in iron-limiting conditions, and all strains, regardless of their serotype, showed a similar pattern of induced proteins. The results of the present study suggest that T. maritimum possesses at least two different systems of iron acquisition: one involving the synthesis of siderophores and another that allows the utilization of heme groups as iron sources by direct binding.