Abstract：
The physiology and ecology of particle-associated marine bacteria are of growing interest, but our knowledge of their aggregation behavior and mechanisms controlling their association with particles remains limited. We have found that a particle-associated isolate, Alteromonas sp. ALT199 strain 4B03, and the related type-strain A. macleodii 27126 both form large (>500 μm) aggregates while growing in rich medium. A non-clumping variant (NCV) of 4B03 spontaneously arose in the lab, and whole-genome sequencing revealed a partial deletion in the gene encoding UDP-glucose-4-epimerase (galEΔ308-324). In 27126, a knock-out of galE (ΔgalE::kmr) resulted in a loss of aggregation, mimicking the NCV. Microscopic analysis shows that both 4B03 and 27126 rapidly form large aggregates, whereas their respective galE mutants remain primarily as single planktonic cells or clusters of a few cells. Strains 4B03 and 27126 also form aggregates with chitin particles, but their galE mutants do not. Alcian Blue staining shows that 4B03 and 27126 produce large transparent exopolymer particles (TEP), but their galE mutants are deficient in this regard. This study demonstrates the capabilities of cell-cell aggregation, aggregation of chitin particles, and production of TEP in strains of Alteromonas, a widespread particle-associated genus of heterotrophic marine bacteria. A genetic requirement for galE is evident for each of the above capabilities, expanding the known breadth of requirement for this gene in biofilm-related processes.
OBJECTIVE: Heterotrophic marine bacteria have a central role in the global carbon cycle. Well-known for releasing CO2 by decomposition and respiration, they may also contribute to particulate organic matter (POM) aggregation, which can promote CO2 sequestration via the formation of marine snow. We find that two members of the prevalent particle-associated genus Alteromonas can form aggregates comprising cells alone or cells and chitin particles, indicating their ability to drive POM aggregation. In line with their multivalent aggregation capability, both strains produce TEP, an excreted polysaccharide central to POM aggregation in the ocean. We demonstrate a genetic requirement for galE in aggregation and large TEP formation, building our mechanistic understanding of these aggregative capabilities. These findings point toward a role for heterotrophic bacteria in POM aggregation in the ocean and support broader efforts to understand bacterial controls on the global carbon cycle based on microbial activities, community structure, and meta-omic profiling.
OBJECTIVE: Heterotrophic marine bacteria have a central role in the global carbon cycle. Well-known for releasing CO2 by decomposition and respiration, they may also contribute to particulate organic matter (POM) aggregation, which can promote CO2 sequestration via the formation of marine snow. We find that two members of the prevalent particle-associated genus Alteromonas can form aggregates comprising cells alone or cells and chitin particles, indicating their ability to drive POM aggregation. In line with their multivalent aggregation capability, both strains produce TEP, an excreted polysaccharide central to POM aggregation in the ocean. We demonstrate a genetic requirement for galE in aggregation and large TEP formation, building our mechanistic understanding of these aggregative capabilities. These findings point toward a role for heterotrophic bacteria in POM aggregation in the ocean and support broader efforts to understand bacterial controls on the global carbon cycle based on microbial activities, community structure, and meta-omic profiling.
摘要：
与颗粒相关的海洋细菌的生理和生态学越来越受到人们的关注，但是我们对它们的聚集行为和控制它们与粒子缔合的机制的了解仍然有限。我们发现一种与粒子相关的分离物，Alteromonassp.ALT199菌株4B03和相关的类型菌株A.macleodii27126都形成大的（>500μm）聚集体，同时在丰富的培养基中生长。4B03的非结块变体（NCV）在实验室中自发出现，全基因组测序显示编码UDP-葡萄糖-4-差向异构酶（galEΔ308-324）的基因部分缺失。在27126中，galE（ΔgalE：：kmr）的敲除导致聚集丧失，模仿NCV。微观分析表明，4B03和27126迅速形成大的聚集体，而它们各自的galE突变体主要保持为单个浮游细胞或几个细胞簇。菌株4B03和27126也与几丁质颗粒形成聚集体，但他们的galE突变体却没有.AlcianBlue染色显示4B03和27126产生大的透明外聚合物颗粒（TEP），但是他们的galE突变体在这方面是有缺陷的。这项研究证明了细胞-细胞聚集的能力，几丁质颗粒的聚集，和在Alteromonas菌株中产生TEP，异养海洋细菌的一种广泛的颗粒相关属。对于上述每种能力，galE的遗传需求都很明显，扩大生物膜相关过程中对该基因的已知需求范围。
目的：异养海洋细菌在全球碳循环中起着核心作用。众所周知，它通过分解和呼吸释放二氧化碳，它们也可能有助于颗粒有机物(POM)聚集，这可以通过海洋雪的形成促进二氧化碳的封存。我们发现，普遍存在的颗粒相关的Alteromonas属的两个成员可以形成包含单独的细胞或细胞和几丁质颗粒的聚集体，表示它们驱动POM聚合的能力。根据它们的多价聚集能力，两种菌株都产生TEP，海洋中POM聚集的排泄多糖。我们证明了galE聚集和大TEP形成的遗传需求，建立我们对这些综合能力的机械理解。这些发现指出了异养细菌在海洋POM聚集中的作用，并支持更广泛的努力，以了解基于微生物活动的细菌对全球碳循环的控制。群落结构,和元组学分析。
目的：异养海洋细菌在全球碳循环中起着核心作用。众所周知，它通过分解和呼吸释放二氧化碳，它们也可能有助于颗粒有机物(POM)聚集，这可以通过海洋雪的形成促进二氧化碳的封存。我们发现，普遍存在的颗粒相关的Alteromonas属的两个成员可以形成包含单独的细胞或细胞和几丁质颗粒的聚集体，表示它们驱动POM聚合的能力。根据它们的多价聚集能力，两种菌株都产生TEP，海洋中POM聚集的排泄多糖。我们证明了galE聚集和大TEP形成的遗传需求，建立我们对这些综合能力的机械理解。这些发现指出了异养细菌在海洋POM聚集中的作用，并支持更广泛的努力，以了解基于微生物活动的细菌对全球碳循环的控制。群落结构,和元组学分析。
