Horizontal transfer of an exopolymer complex from one bacterial species toanother

Alasan, the exocellular polymeric emulsifier produced by Acinetobacter radi oresistens KA53 was shown to bind to the surface of Sphingomonas paucimobil is EPA505 and Acinetobacter calcoaceticus RAG-1. The presence of alasan on the surface of S. paucimobilis EPA505 and A. calcoaceticus RAG-1 caused a d ecrease in their cell-surface hydrophobicities. Binding was proportional to the concentration of recipient cells and input alasan. At the highest conc entration of A. calcoaceticus RAG-1 (4 x 10(9) ml(-1)) and alasan (20 mu g ml(-1)) tested, 75% of the alasan was cell bound. Alasan binding was measur ed by the loss of emulsifying activity and alasan protein and polysaccharid e from the aqueous phase after incubation of alasan with the recipient cell s. In addition, alasan was visualized on the surface of the recipient cells by staining with anti-alasan antibodies and rhodamine-labelled secondary a ntibodies. Moreover, when the alasan-producing A. radioresistens KA53 was g rown together with A. calcoaceticus RAG-1, alasan was released from the pro ducing strain and became bound to the recipient RAG-1 cells, as demonstrate d by fluorescence microscopy. This horizontal transfer of exopolymers from one bacterial species to another has significant implications in natural mi crobial communities, coaggregation and biofilms.