Development and Dynamics of Pseudomonas sp. Biofilms

Abstract

Pseudomonas sp. strain B13 and Pseudomonas putida OUS82 were genetically tagged with the green fluorescent protein and the Discosoma sp. red fluorescent protein, and the development and dynamics occurring in flow chamber-grown two-colored monospecies or mixed-species biofilms were investigated by the use of confocal scanning laser microscopy. Separate red or green fluorescent microcolonies were formed initially, suggesting that the initial small microcolonies were formed simply by growth of substratum attached cells and not by cell aggregation. Red fluorescent microcolonies containing a few green fluorescent cells and green fluorescent microcolonies containing a few red fluorescent cells were frequently observed in both monospecies and two-species biofilms, suggesting that the bacteria moved between the microcolonies. Rapid movement of P. putida OUS82 bacteria inside microcolonies was observed before a transition from compact microcolonies to loose irregularly shaped protruding structures occurred. Experiments involving a nonflagellated P. putida OUS82 mutant suggested that the movements between and inside microcolonies were flagellum driven. The results are discussed in relation to the prevailing hypothesis that biofilm bacteria are in a physiological state different from planktonic bacteria.Surface adhesion of bacteria and subsequent cell binary fission and exopolymer production lead to the formation of bacterial biofilms (see reference 6 for a review). Application of confocal scanning laser microscopy (CSLM) has led to the suggestion that microcolonies are the basic structural units in sessile communities (4). It was found that biofilms are highly hydrated open structures containing a high fraction of exopolymers and large void spaces between the microcolonies (18). Mushroom-shaped microcolonies, separated by channels and voids, were observed in Pseudomonas fluorescens biofilms (15, 16). Investigations of multispecies biofilm communities on granular activated carbon in fluidized-bed reactors revealed that growth occurred as discrete microcolony structures separated by channel boundaries (19). Microbial biofilms in river water were shown to have a ridged structure, with microcolonies forming ridges parallel to the direction of flow (23).Evidence is now emerging that motility may play a role in structure formation in biofilms. After the initial attachment to the substratum, Pseudomonas aeruginosa evidently moves on the substratum by means of twitching motility, and it has been suggested that the initial microcolonies are formed by aggregation of bacteria (25). Furthermore, it has been suggested that the initial microcolonies in Vibrio cholerae El Tor biofilms are formed via flagellar motility of the cells along the substratum (32). In addition, Wolfaardt et al. (34) and Nielsen et al. (24) observed structural changes in biofilms in response to changing environments, suggesting that established biofilms in some cases may display dynamic behavior. Since it appears that structures in both young and mature biofil...

Biodegradation of Low Density Polythene (LDPE) by Pseudomonas Species

“…It was further noticed that the biofilm cells and planktonic cells show very slow changes in growth over a period of time. These results are consistent with earlier observations of Tolker-Nielsen et al [9] who reported that Pseudomonas spp. have slow rate of microcolony formation when compared to other microorganisms.…”

Attachment to and biofilm formation on abiotic surfaces by Acinetobacter baumannii: involvement of a novel chaperone-usher pili assembly system

“…Cell motility and the presence of cellular appendages have been implicated in the formation of biofilms by other bacteria (O'Toole & Kolter, 1998a;Tolker-Nielsen et al, 2000). However, members of the Acinetobacter genus, including A. baumannii, are taxonomically defined to lack flagella and thus are non-motile .…”

“…Previous research efforts have shown that biofilm formation proceeds via a series of steps which, upon completion, produce a mature, three-dimensional structure on both biotic and abiotic surfaces. Some of the current working models for biofilm formation implicate the participation of either bacterial surface motility mediated by pili and flagella (O'Toole & Kolter, 1998a), the flagellummediated recruitment of planktonic cells by the developing biofilm from the liquid medium (Tolker-Nielsen et al, 2000) or the formation and growth of microcolonies formed as a consequence of the multiplication of cells attached to solid surfaces (Heydorn et al, 2000). While forming and establishing these multicellular structures, the cells composing them secrete exopolysaccharides which serve to fortify and maintain the structure of the biofilm.…”

Bacterial swimmers that infiltrate and take over the biofilm matrix

“…Bacterial flagella were previously reported to have a positive role in nascent biofilm maturation and spreading (e.g., Bacillus subtilis, Pseudomonas sp.) (8,9). However, motile cells in mature biofilms have thus far been described as arising from a late-stage differentiation event (e.g., within hollow voids of Pseudomonas aeruginosa mushroom-like structures) and being involved in dispersion of mature biofilms (10).…”