Microorganisms associated with Chara hispida L. show a high antagonistic potential towards bacteria

Members of the genus Chara are multi-cellular green-alga, common lake inhabitants and fulfil important functions in these ecosystems. Little is known about the associated microorganisms of these abundant water inhabitants. To analyse bacteria and fungi associated with Chara, samples of Chara hispida L. (Bristly Stonewort) were taken from lakes in Mecklenburg-Pomerania (Germany) and analysed by a polyphasic approach including cultivation-dependent and independent techniques. The stoneworts were colonised by bacteria in high (3×104-4×105 CFU g-1 fw) and by fungi (102 CFU g-1 fw) in much lower abundances. In general, the isolates showed a low antagonistic potential against fungi (2%); only four out of 180 showed activities against Verticillium dahliae. In contrast, a higher proportion of isolates (21%) was active against Xanthomonas campestris. In addition, some antagonists obtained displayed a high antagonistic potential against cyanobacteria and no potential against Bacillariophyta. Representatives of each ARDRA group were identified by partial sequencing of the 16S rRNA. Pseudomonas fluorescens, Pseudomonas graminis, Enterobacter amnigenus, Pantoea agglomerans and Bacillus spp. were identified as prominent antibacterial antagonists. Comparing the microbial community and single antagonistic isolates by SSCP (single strand conformation polymorphism analysis), we found a high diversity of Chara-associated bacterial communities and bacterial-antagonists as dominant members of them.