Cell Death in Pseudomonas aeruginosa Biofilm Development

Abstract

Bacteria growing in biofilms often develop multicellular, three-dimensional structures known as microcolonies. Complex differentiation within biofilms of Pseudomonas aeruginosa occurs, leading to the creation of voids inside microcolonies and to the dispersal of cells from within these voids. However, key developmental processes regulating these events are poorly understood. A normal component of multicellular development is cell death. Here we report that a repeatable pattern of cell death and lysis occurs in biofilms of P. aeruginosa during the normal course of development. Cell death occurred with temporal and spatial organization within biofilms, inside microcolonies, when the biofilms were allowed to develop in continuous-culture flow cells. A subpopulation of viable cells was always observed in these regions. During the onset of biofilm killing and during biofilm development thereafter, a bacteriophage capable of superinfecting and lysing the P. aeruginosa parent strain was detected in the fluid effluent from the biofilm. The bacteriophage implicated in biofilm killing was closely related to the filamentous phage Pf1 and existed as a prophage within the genome of P. aeruginosa. We propose that prophage-mediated cell death is an important mechanism of differentiation inside microcolonies that facilitates dispersal of a subpopulation of surviving cells.

The cidA murein hydrolase regulator contributes to DNA release and biofilm development in Staphylococcus aureus

“…Given that cell death and lysis are important during biofilm development in other organisms (38)(39)(40), we compared the in vitro biofilm-forming ability of UAMS-1 and KB1050 when grown for 24 h in a static biofilm assay (Fig. 2).…”

Evolutionary and population dynamics: A coupled approach

“…For example, in the presence of antibiotics, this downgraded metabolism can make bacteria less vulnerable leading to persistence [87][88][89][90], or dormancy might hedge a population against strongly fluctuating environments [86,90,91]. Second, environmental conditions can lead to death rates increasing with the population size N while birth rates are only slightly affected [92]. The population, therefore, reaches a state of dynamical maintained population size with the death rates exactly balancing the birth rates (scenario of balanced growth).…”

Phage-induced lysis enhances biofilm formation in Shewanella oneidensis MR-1

“…Mutants lacking the phage form smaller colonies during the first days of biofilm formation and a potential role of phage-mediated cell lysis in eDNA release has been discussed but has not directly been demonstrated (Allesen-Holm et al, 2006;Rice et al, 2009). At later stages of biofilm development, Pf4 is thought to convert into a superinfective lytic form that causes cell death and hollowing of the structures, and, by that, significantly contributes to seeding dispersal of the community (Webb et al, 2003;Rice et al, 2009). In addition, Pf4 has been linked to phenotypic variations in the dispersed cells, leading to small-colony variants that are characterized by accelerated biofilm formation (Webb et al, 2004;Rice et al, 2009).…”