Intergeneric Coaggregation among Drinking Water Bacteria: Evidence of a Role for Acinetobacter calcoaceticus as a Bridging Bacterium

Abstract

Intergeneric coaggregation of drinking water bacteria was tested. Acinetobacter calcoaceticus was found not only to autoaggregate but also to coaggregate with four of the five other isolates (Burkholderia cepacia, Methylobacterium sp., Mycobacterium mucogenicum, Sphingomonas capsulata, and Staphylococcus sp.). In its absence, no coaggregation was found. Interactions were lectin-saccharide mediated. The putative bridging function of A. calcoaceticus was evidenced by multispecies biofilm studies, through a strain exclusion process.The development of microbial biofilm communities results from a series of processes, including initial surface association and adherence, subsequent multiplication of the constituent organisms, the adherence of other species, and the production of extracellular polymeric substances (17). Many of these events are well described (14,17). The bacterial surface properties coaggregation and coadhesion, along with interspecies relationships, are believed to play a determinant role in the formation of multispecies biofilms in drinking water distribution systems (11,13). Nevertheless, the function of coaggregation in the initial development of biofilms still remains unclear. This adhesion mechanism is highly specific and conveys advantages to microorganisms, including the transfer of chemical signals, exchange of genetic information, protection from adverse environmental conditions, and metabolic cooperation between different species as well as cell differentiation in some populations (18). Coaggregation is mediated by protein-saccharide interactions and blocked by simple sugars (1, 2). Coaggregation interactions contribute to the development of biofilms via the specific recognition and adhesion of single suspended cells to genetically distinct bacteria in a developing biofilm and/or by the subsequent adhesion of previously coaggregated secondary colonizers to the developing biofilm. In both cases, bacterial cells in suspension specifically adhere to those within biofilms through a coadhesion process (12). This study describes the intergeneric coaggregation of six heterotrophic bacteria isolated from drinking water and investigates the roles of surface proteins and saccharides in the coaggregation process. Acinetobacter calcoaceticus was investigated as a bridging organism in drinking water biofilms.Coaggregation assays were performed with six representative drinking water bacteria, Acinetobacter calcoaceticus, Burkholderia cepacia, Methylobacterium sp., Mycobacterium mucogenicum, Sphingomonas capsulata, and Staphylococcus sp. The bacteria were isolated, identified by 16S rRNA gene sequencing, and cultivated according to the method of Simões et al. (13). The stationary phase of growth was selected for coaggregation studies (9), and cells from planktonic batch cultures were harvested by centrifugation (20 min at 13,000 ϫ g), washed three times, and resuspended in sterile tap water. A visual coaggregation assay, with some modifications from the method of Cisar et al. (2), was used. Briefly, bacte...

Pyrosequencing analysis of eukaryotic and bacterial communities in faucet biofilms

“…These demonstrated the importance of Alphaproteobacteria and Betaproteobacteria in oligotrophic DWDS ecosystems. The majority of Alphaproteobacteria sequences belonged to the orders Sphingomonadales (18.58-38.67%) and Rhizobiales (6.20-29.12%), and mainly classified into the genera Bradyrhizobium, Blastomonas, Methylobacterium, Novosphingobium, Porphyrobacter, Sphingobium, Sphingomonas, and Sphingopyxis, most members of which are common residents of fresh water habitats or potable water distribution systems (Hong et al, 2010;Liu et al, 2012;Simoes et al, 2008). Many Sphingomonadales bacteria can produce abundant exopolysaccharides, lack special growth requirements, and resist to chlorine (Furuhata et al, 2007), characteristics which conferred an ecological advantage for their growth and formation of stable biofilms in oligotrophic environments (White et al, …”

Molecular analysis of long-term biofilm formation on PVC and cast iron surfaces in drinking water distribution system

“…Only 28 OTUs were shared by all of them (Fig. 3), mainly falling into the orders Rhizobiales, Sphingomonadales, Burkholderiales, and Pseudomonadales, most members of which were common residents in fresh water habitats or biofilms in water distribution systems (Liu et al, 2012b;Simoes et al, 2008). β-Proteobacteria (24.14%) was the second largest bacterial group in the cast iron biofilm community, followed by γ-Proteobacteria (16.81%), Bacteroidetes (6.02%), Planctomycetes (2.16%), and Actinobacteria (2.02%), whereas Actinobacteria (5.82%) was the second most dominant group in the PVC biofilm, followed by γ-Proteobacteria (2.45%) (Fig.…”

A Keystone Methylobacterium Strain in Biofilm Formation in Drinking Water

“…Among culturable bacteria, the most commonly found genera in drinking water are Pseudomonas [5][6][7][8][9][10][11], Sphingomonas [4,[6][7][8]10,12], Methylobacterium [4,[6][7][8]12], Aeromonas [8,13], and Acinetobacter [5,6,8]. A small number of species, such as the Methylobacterium species [12], Acinetobacter calcoaceticus [4], and Mycobacterium species [12,14] have been implicated in promoting aggregation in pure or simple mixed cultures.…”

“…This adhesion mechanism has been suggested to influence the formation of complex multi-species biofilms in several diverse habitats [3]. Aggregation conveys many advantages to microorganisms in drinking water systems, such as enhanced transfer of chemical signals, exchange of genetic information, protection against harsh conditions, and metabolic cooperation [4].…”

“…A small number of species, such as the Methylobacterium species [12], Acinetobacter calcoaceticus [4], and Mycobacterium species [12,14] have been implicated in promoting aggregation in pure or simple mixed cultures. Species of Methylobacterium are found in a wide variety of environments, such as soil, dust, freshwater, lake sediments, leaf surfaces, air, root nodules, rice grains, and hospital environments [15].…”