Plant Ecophysiology, Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
Environ Microbiol. 2011 Apr;13(4):1052-63. doi: 10.1111/j.1462-2920.2010.02411.x. Epub 2011 Jan 18.
Phototrophic epilithic biofilms harbour a distinct assemblage of heterotrophic bacteria, cyanobacteria and photoautotrophic algae. Secretion of extracellular polymeric substances (EPS) by these organisms and the physicochemical properties of the EPS are important factors for the development of the biofilms. We have isolated representative diatom and bacteria strains from epilithic biofilms of Lake Constance. By pairwise co-cultivating these strains we found that diatom growth and EPS secretion by diatoms may depend on the presence of individual bacteria. Similar results were obtained after addition of spent bacterial medium to diatom cultures, suggesting that soluble substances from bacteria have an impact on diatom physiology. While searching for putative bacterial signal substances, we found that concentrations of various dissolved free amino acids (DFAA) within the diatom cultures changed drastically during co-cultivation with bacteria. Further, the secretion of extracellular carbohydrates and proteins can be influenced by bacteria or their extracellular substances. We have performed mass spectrometric peptide mapping to identify proteins which are secreted when co-cultivating the diatom Phaeodactylum tricornutum Bohlin and Escherichia coli. The identified proteins are possibly involved in signalling, extracellular carbohydrate modification and uptake, protein and amino acid modification, and cell/cell aggregation of diatom and bacteria strains. Our data indicate that diatom-bacteria biofilms might be regulated by a complex network of chemical factors involving EPS, amino acid monomers and other substances. Thus interactions with bacteria can be considered as one of the main factors driving biofilm formation by benthic diatoms.
光养附生生物膜中栖息着独特的异养细菌、蓝藻和光能自养藻类组合。这些生物分泌的细胞外多聚物（EPS）及其 EPS 的理化性质是生物膜形成的重要因素。我们已经从康斯坦茨湖的附生生物膜中分离出具有代表性的硅藻和细菌菌株。通过成对共培养这些菌株，我们发现硅藻的生长和 EPS 分泌可能依赖于个别细菌的存在。将细菌用过的培养基添加到硅藻培养物中也得到了类似的结果，这表明细菌的可溶性物质对硅藻的生理有影响。在寻找潜在的细菌信号物质时，我们发现各种游离氨基酸（DFAA）在与细菌共培养过程中，硅藻培养液中的浓度会发生剧烈变化。此外，细菌或其细胞外物质可以影响细胞外碳水化合物和蛋白质的分泌。我们进行了质谱肽图谱分析，以鉴定当共培养硅藻 Phaeodactylum tricornutum Bohlin 和大肠杆菌时分泌的蛋白质。鉴定出的蛋白质可能参与信号转导、细胞外碳水化合物修饰和摄取、蛋白质和氨基酸修饰以及硅藻和细菌菌株的细胞/细胞聚集。我们的数据表明，硅藻-细菌生物膜可能受到涉及 EPS、氨基酸单体和其他物质的复杂化学因素网络的调节。因此，与细菌的相互作用可以被视为驱动底栖硅藻生物膜形成的主要因素之一。
