Willsey Graham G, Wargo Matthew J
Department of Microbiology and Molecular Genetics, University of Vermont College of Medicine, Burlington, Vermont, United States of America.
PLoS One. 2015 Nov 23;10(11):e0143617. doi: 10.1371/journal.pone.0143617. eCollection 2015.
Bacteria secrete enzymes into the extracellular space to hydrolyze macromolecules into constituents that can be imported for microbial nutrition. In bacterial communities, these enzymes and their resultant products can be modeled as community property. Our goal was to investigate the impact of individual community member absence on the resulting community production of exoenzymes (extracellular enzymes) involved in lipid and protein hydrolysis. Our model community contained nine bacteria isolated from the potable water system of the International Space Station. Bacteria were grown in static conditions individually, all together, or in all combinations of eight species and exoproduct production was measured by colorimetric or fluorometric reagents to assess short chain and long chain lipases, choline-specific phospholipases C, and proteases. The exoenzyme production of each species grown alone varied widely, however, the enzyme activity levels of the mixed communities were functionally robust to absence of any single species, with the exception of phospholipase C production in one community. For phospholipase C, absence of Chryseobacterium gleum led to increased choline-specific phospholipase C production, correlated with increased growth of Burkholderia cepacia and Sphingomonas sanguinis. Because each individual species produced different enzyme activity levels in isolation, we calculated an expected activity value for each bacterial mixture using input levels or known final composition. This analysis suggested that robustness of each exoenzyme activity is not solely mediated by community composition, but possibly influenced by bacterial communication, which is known to regulate such pathways in many bacteria. We conclude that in this simplified model of a drinking water bacterial community, community structure imposes constraints on production and/or secretion of exoenzymes to generate a level appropriate to exploit a given nutrient environment.
细菌将酶分泌到细胞外空间，将大分子水解成可被微生物摄取用于营养的成分。在细菌群落中，这些酶及其产生的产物可被视为群落特性。我们的目标是研究单个群落成员缺失对参与脂质和蛋白质水解的胞外酶（细胞外酶）的群落产生的影响。我们的模型群落包含从国际空间站饮用水系统中分离出的9种细菌。细菌分别在静态条件下单独培养、一起培养，或在8种细菌的所有组合中培养，通过比色或荧光试剂测量胞外产物的产生，以评估短链和长链脂肪酶、胆碱特异性磷脂酶C和蛋白酶。单独培养的每种细菌的胞外酶产生差异很大，然而，除了一个群落中磷脂酶C的产生外，混合群落的酶活性水平在功能上对任何单个物种的缺失都具有稳健性。对于磷脂酶C，缺失沼泽金黄杆菌导致胆碱特异性磷脂酶C的产生增加，这与洋葱伯克霍尔德菌和血鞘氨醇单胞菌的生长增加相关。由于每个单独的物种在单独培养时产生不同的酶活性水平，我们使用输入水平或已知的最终组成计算每种细菌混合物的预期活性值。该分析表明，每种胞外酶活性的稳健性不仅由群落组成介导，还可能受细菌间通讯的影响，已知细菌间通讯在许多细菌中调节此类途径。我们得出结论，在这个简化的饮用水细菌群落模型中，群落结构对胞外酶的产生和/或分泌施加限制，以产生适合利用给定营养环境的水平。
