Taxonomic and Bioactivity Characterizations of Mameliella alba Strain LZ-28 Isolated from Highly Toxic Marine Dinoflagellate Alexandrium catenella LZT09.

Microalgae host varied microbial consortium harboring cross-kingdom interactions with fundamental ecological significance in aquatic ecosystems. Revealing the complex biofunctions of the cultivable bacteria of phycosphere microbiota is one vital basis for deeply understanding the mechanisms governing these dynamic associations. In this study, a new light-yellow pigmented bacterial strain LZ-28 was isolated from the highly-toxic and harmful algal bloom-forming dinoflagellate Alexandrium catenella LZT09. Collective phenotypic and genotypic profiles were obtained to confidently identify this strain as a new Mameliellaalba member. Comparative genomic analysis showed that strain LZ-28 shared highly similar functional features with other four marine algae-derived M. alba strains in spite of their distinctive isolation sources. Based on the bioactivity assaying, the mutual growth-promoting effects between bacterial strain LZ-28 and algal strain LZT09 were observed. After the culture conditions were optimized, strain LZ-28 demonstrated an extraordinary production ability for its bioflocculanting exopolysaccharides (EPS). Moreover, the portions of two monosaccharides glucose and fucose of the EPS were found to positively contribute to the bioflocculanting capacity. Therefore, the present study sheds light on the similar genomic features among the selected M. alba strains, and it also reveals the potential pharmaceutical, environmental and biotechnological implications of active EPS produced by this new Mameliella alba strain LZ-28 recovered from toxic bloom-forming marine dinoflagellate.

[Amino acids in marine particulate matters and sediments and their role as indicators for organic matter degradation.] / 海洋颗粒物/æ²‰ç§¯ç‰©ä¸­çš„æ°¨åŸºé ¸åŠå ¶å¯¹æœ‰æœºè´¨é™è§£çš„æŒ‡ç¤ºä½œç”¨.

As important components of marine organic matters especially of organic nitrogen, amino acids play an important role in organic matter cycles owing to their lability. The concentration, composition, and distribution of amino acids have been widely used to indicate the degradation state of organic matters in particulates and sediments of marine. Here, the distribution, influencing factors of amino acids and their role in indicating degradation of organic matters were systematically summarized. Gly, Glu, Ala, and Asp were the major components of amino acids in marine particulates and sediments. The contents of amino acids in the particles and sediments showed a decreasing tendency from the coastal waters to the open sea, and adecreased with the water depth. The lower value of %AA-C/TOC, %AA-N/TN and degradation index (DI) based on changes in the composition of amino acids indicated the higher degradation degrees of organic matters. The reactivity index (RI) and ratios of D-AA and L-AA (D/L) based on non-protein amino acids and D-AA were used to indicate the degradation of organic matter according to the bacterial transformation of amino acids, in which RI value closer to 0, higher D/L, and lower ratios of protein amino acids to non-protein amino acids (Asp/ß-Ala and Glu/γ-Aba) indicated the higher degree of degradation in organic matters. The migration and transformation of amino acid were mainly affected by dissolved oxygen, nutrient concentrations, sources of organic matter, depositional environments and microbial activities. Further studies should focus on the synergistic effects of particles and sediments, and also the effects and the specific regulatory roles of microorganisms on amino acids.