Dipartimento di Scienze Ecologiche e Biologiche, University of Tuscia, Viterbo, Italy.
Microb Cell Fact. 2013 Jan 29;12:10. doi: 10.1186/1475-2859-12-10.
Marine environments are the widest fonts of biodiversity representing a resource of both unexploited or unknown microorganisms and new substances having potential applications. Among microbial products, exopolysaccharides (EPS) have many physiological functions and practical applications. Since EPS production by many bacteria is too scarce for practical use and only few species are known for their high levels of production, the search of new high EPS producers is of paramount importance. Many marine bacteria, that produce EPS to cope with strong environmental stress, could be potentially exploited at the industrial level.
A novel bacterium, strain BM39, previously isolated from sediments collected in the Tyrrhenian Sea, was selected for its production of very high levels of EPS. BM39 was affiliated to Pantoea sp. (Enterobacteriaceae) by 16S rRNA gene sequencing and biochemical tests. According to the phylogenetic tree, this strain, being quite far from the closest known Pantoea species (96% identity with P. agglomerans and P. ananatis) could belong to a new species. EPS production was fast (maximum of ca. 21 g/L in 24 h on glucose medium) and mainly obtained during the exponential growth. Preliminary characterization, carried out by thin layer and gel filtration chromatography, showed that the EPS, being a glucose homopolymer with MW of ca. 830 kDa, appeared to be different from those of other bacteria of same genus. The bacterium showed a typical slightly halophilic behavior growing optimally at NaCl 40 ‰ (growing range 0-100 ‰). Flow cytometry studies indicated that good cell survival was maintained for 24 h at 120 ‰. Survival decreased dramatically with the increase of salinity being only 1 h at 280 ‰. The biochemical characterization, carried out with the Biolog system, showed that MB39 had a rather limited metabolic capacity. Its ability, rather lower than that of P. agglomerans, was almost only confined to the metabolization of simple sugars and their derivatives. Few alcohols, organic acids and nitrogen compounds were partially used too.
Strain BM39, probably belonging to a new species, due to its remarkable EPS production, comparable to those of known industrial bacterial producers, could be suggested as a new microorganism for industrial applications.
海洋环境是生物多样性的最大来源，代表着未开发或未知微生物资源和具有潜在应用的新物质的资源。在微生物产物中，胞外多糖（EPS）具有许多生理功能和实际应用。由于许多细菌产生 EPS 的量太少，无法实际应用，而且只有少数几种细菌因其高水平的生产而被人们所知，因此寻找新的高产 EPS 的细菌至关重要。许多产生 EPS 以应对强烈环境压力的海洋细菌，可能具有在工业水平上被开发的潜力。
从收集自第勒尼安海沉积物中分离到的一株新型细菌 BM39，因其能产生非常高水平的 EPS 而被选中。BM39 通过 16S rRNA 基因测序和生化试验被鉴定为 Pantoea sp.（肠杆菌科）。根据系统发育树，该菌株与最近已知的 Pantoea 种（与 P. agglomerans 和 P. ananatis 的同源性为 96%）相差较远，可能属于一个新种。EPS 的生产速度很快（在葡萄糖培养基上 24 小时内最大可达约 21 g/L），主要在指数生长期获得。通过薄层和凝胶过滤色谱进行的初步表征表明，EPS 是一种葡萄糖均聚物，分子量约为 830 kDa，与同属的其他细菌的 EPS 不同。该细菌表现出典型的微嗜盐行为，在 40‰NaCl 下最佳生长（生长范围为 0-100‰）。流式细胞术研究表明，在 120‰下 24 小时内可以保持良好的细胞存活率。随着盐度的增加，存活率急剧下降，在 280‰时仅能存活 1 小时。使用 Biolog 系统进行的生化特性分析表明，BM39 的代谢能力相当有限。其能力，几乎仅局限于简单糖及其衍生物的代谢，与 P. agglomerans 相比，要低得多。一些醇、有机酸和含氮化合物也被部分利用。
由于其显著的 EPS 产量，与已知的工业细菌生产菌相当，菌株 BM39 可能属于一个新种，可被推荐为一种新的工业应用微生物。
