Ecology of mixed biofilms subjected daily to a chlorinated alkaline solution: spatial distribution of bacterial species suggests a protective effect of one species to another

Abstract

Three bacterial strains (Kocuria sp. C714.1, Brevibacterium linens B337.1 and Staphylococcus sciuri CCL101) were grown together on stainless steel and were subjected daily to a commercial alkaline chlorine solution (22 mg l-1 of free chlorine, pH 11) over a period of 4 weeks. After the daily chemical shock, culture madia [1:20 dilution of tryptic soy broth (TSB-YE/20) or diluted whey] was deposited on the biofilms. The chemical shocks led first to a drop in the culturable population, followed by an increase and finally stabilization at around 106-107 CFU cm-2 by day 11 of the experiment. These changes in the microbial population can be attributed to a decreasing susceptibility to the antimicrobial agent with biofilm age, and to the consumption of free chlorine by biofilm exoproteins. The microbial composition appeared to be linked to the free chlorine concentration that depended on exoprotein production. At the end of the experiment, exoprotein production was greater for biofilms grown in TSBYE/20 than in whey. As a consequence, biofilms grown in whey did not neutralize the chlorine and the dominant strain was the one having the highest resistance to chlorine: K. varians. When biofilm were grown in TSBYE/20, chlorine was neutralized and the dominant strain was the one having the highest growth rate: S. sciuri. The presence of chlorine may also explain the distribution of S. sciuri cells as a ring around Kocuria sp. microcolonies. When chlorine was totally consumed by the biofilm during the chemical shock, S. sciuri was no longer grouped around Kocuria sp. microcolonies but was evenly scattered over the substratum as single cells or in small clusters, as it was before any chemical treatment. These findings strongly suggest protection of S. sciuri by Kocuria sp. microcolonies against the chlorinated solution. This phenomenon, added to the low susceptibility phenotype of the biofilm cells, could at least partly explain the survival of microbial cells in an adverse environment.

Microbiota formed on attached stainless steel coupons correlates with the natural biofilm of the sink surface in domestic kitchens

“…The genus has also been isolated from other food production environments (Carpentier and Chassaing 2004;Møretrø et al 2011Møretrø et al , 2013. Survival in these environments can be explained by resistance to desiccation, biofilm-forming abilities, and tolerance to chlorine (Leriche et al 2003;Møretrø et al 2013). Others have shown that K. rhizophila can survive on dry surfaces for several days and has tolerance to high-salt concentrations in growth medium (Kovacs et al 1999;Kim et al 2004).…”

Enhanced Biofilm Formation and Increased Resistance to Antimicrobial Agents and Bacterial Invasion Are Caused by Synergistic Interactions in Multispecies Biofilms

“…However, in several studies, of which the majority focused on biofilms in the oral cavity, it has been demonstrated that different bacterial species in biofilms affect one another positively as well as negatively. Interactions beneficial to one or more strains or species include coaggregation of cells (37,42,47,59), conjugation (17), and protection of one or several species from eradication when the biofilm is exposed to antimicrobial compounds (7,13,27). Such protection may be caused by a variety of factors, including enzyme complementation (48) and organized spatial distribution of the cells in the biofilm (7,27).…”

“…Interactions beneficial to one or more strains or species include coaggregation of cells (37,42,47,59), conjugation (17), and protection of one or several species from eradication when the biofilm is exposed to antimicrobial compounds (7,13,27). Such protection may be caused by a variety of factors, including enzyme complementation (48) and organized spatial distribution of the cells in the biofilm (7,27). These and other mechanisms are likely to deliver synergistic effects that result in cooperative biofilm formation by strains that were unable to form a biofilm alone (14,17,38).…”

Identification of a c-di-GMP-Regulated Polysaccharide Locus Governing Stress Resistance and Biofilm and Rugose Colony Formation in Vibrio vulnificus

“…Biofilms provide a stable, protective milieu for growth and a means to facilitate transmission by acting as a source for the dissemination of large numbers of microorganisms (30,43,84). Compared with their planktonic counterparts, biofilm consortia are extraordinarily resistant to antibiotics, biocides, and the immune defense responses of the host.…”