Bacterial chitin utilisation at extremely haloalkaline conditions
Bacterial chitin utilisation at extremely haloalkaline conditions
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DOI：
10.1007/s00792-012-0484-6
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发表时间：
2012-11-01
期刊：
影响因子：
2.9
通讯作者：
Ravin, N. V.
中科院分区：
文献类型：
--
作者：
Sorokin, D. Y.;Tourova, T. P.;Ravin, N. V.
由于卤虾蒿的高生物量产量，在pH值为中性的高盐生境中会大量产生几丁质。最近，在Kulunda Steppe （Altai, Russia）的高盐碱水湖泊中也发现了大量的Artemia，这促使我们研究了在极端盐碱性条件下微生物利用几丁质的可能性。大多数支持甲壳素利用的活性微生物生长在pH 10和高达3.5 M总Na+的厌氧条件下。在好氧条件下，甲壳素的降解较慢，在总Na+ < 2 M时大多不完全和活跃，尽管在4 M Na+时可能发生非常缓慢的部分降解。pH值为10的厌氧富集产生了两组专性嗜卤嗜碱的发酵厌氧菌，专门利用不溶性几丁质作为唯一的生长基质。一组是在中等盐度下生长的单个菌株，另一组是在3.5 M Na+下生长的多个菌株。这些群体代表了两个新的细菌门，与任何其他培养的细菌都没有密切的关系。湖泊沉积物的好氧富集主要由γ变形菌门中海洋微生物属的几个专性嗜盐菌属成员控制。与厌氧菌相比，它们的特化程度较低，在pH为10至2.5 M Na+的环境中，它们与几丁质及其单体和低聚物一起生长。此外，从碱湖沉积物和周围的碱土中分离出了几丁质溶解菌属杆菌和放线菌。总的来说，结果表明，在高盐苏打生境中存在一个活跃和多样化的亲卤碱性几丁质降解微生物群落。
Chitin is produced in large amounts in hypersaline habitats with neutral pH due to the high biomass production of brine shrimp Artemia. Recently, a high abundance of Artemia was also noticed in hypersaline soda lakes in the Kulunda Steppe (Altai, Russia), which prompted us to survey the possibility of microbial chitin utilization at extremely haloalkaline conditions in soda brines. Most active chitin utilisation-supporting microbial growth was found at anaerobic conditions at pH 10 and up to 3.5 M total Na+. At aerobic conditions, the degradation of chitin was slower, mostly incomplete and active at < 2 M total Na+, although very slow partial degradation was possible up to 4 M Na+. Anaerobic enrichments at pH 10 yielded two different groups of obligately haloalkaliphilic fermentative anaerobes, exclusively specialized to utilise insoluble chitin as the only growth substrate. One group was represented by a single strain growing at moderate salinity, and another comprised multiple isolates growing up to 3.5 M Na+. These groups represent two novel bacterial phyla not closely related to any other cultured bacteria. Aerobic enrichments from the lake sediments were dominated by several obligately haloalkaliphilic members of the genus Marinimicrobium in the Gammaproteobacteria. They were less specialised than the anaerobes and grew with chitin and its monomer and oligomers at a pH of 10 up to 2.5 M Na+. Furthermore, several strains of haloalkaliphilic Gram-positive chitinolytics belonging to bacilli and actinobacteria were isolated from soda lake sediments and surrounding soda soils. In general, the results indicate the presence of an active and diverse haloalkaliphilic chitinolytic microbial community in hypersaline soda habitats.