In Situ Biomineralization and Particle Deposition Distinctively Mediate Biofilm Susceptibility to Chlorine

Abstract

Microbial biofilms and mineral precipitation commonly co-occur in engineered water systems, such as cooling towers and water purification systems, and both decrease process performance. Microbial biofilms are extremely challenging to control and eradicate. We previously showed that in situ biomineralization and the precipitation and deposition of abiotic particles occur simultaneously in biofilms under oversaturated conditions. Both processes could potentially alter the essential properties of biofilms, including susceptibility to biocides. However, the specific interactions between mineral formation and biofilm processes remain poorly understood. Here we show that the susceptibility of biofilms to chlorination depends specifically on internal transport processes mediated by biomineralization and the accumulation of abiotic mineral deposits. Using injections of the fluorescent tracer Cy5, we show that Pseudomonas aeruginosa biofilms are more permeable to solutes after in situ calcite biomineralization and are less permeable after the deposition of abiotically precipitated calcite particles. We further show that biofilms are more susceptible to chlorine killing after biomineralization and less susceptible after particle deposition. Based on these observations, we found a strong correlation between enhanced solute transport and chlorine killing in biofilms, indicating that biomineralization and particle deposition regulate biofilm susceptibility by altering biocide penetration into the biofilm. The distinct effects of in situ biomineralization and particle deposition on biocide killing highlight the importance of understanding the mechanisms and patterns of biomineralization and scale formation to achieve successful biofilm control.T he development of biofilms in engineered water systems is usually detrimental. Excessive biofilm growth decreases process performance; for example, it reduces the heat exchange efficiency in cooling towers and hinders the flow through high-pressure water treatment membranes (1, 2). Biofilms in water systems are also potential reservoirs of human pathogens (2-6). Biofilms are difficult to eradicate because they are much less susceptible to antimicrobials and biocides than suspended microbial cells (7,8). The decreased susceptibility of biofilms to biocides results from a combination of the decreased penetration of solutes into the biofilm structure, the protection provided by extracellular polymers, reduced cellular metabolism within biofilms, and the development of resistant cellular phenotypes (persisters) (9-11). Chlorine is one of the most commonly used biocides for biofilm control in engineered water systems (12, 13). Prior studies have found that the limited transport of chlorine to the interior of biofilms reduces the overall killing efficacy of chlorination (12,14).Biofilm biofouling is often associated with the formation of scale, which is an inorganic mineral precipitate that commonly includes calcium carbonate, sulfate, and phosphate (1, 15, 16). The co-occurrence of a biofi...

Current insights into the mechanisms and management of infection stones

“…Unsurprisingly, the formation and physical characteristics of infection stones differ substantially from those formed in the absence of bacteria 55 . Differences in struvite crystal formation under varying conditions have previously been observed [56][57][58][59][60][61] ; crystallization in the presence of bacteria seems to lead to the formation of crystals with defined faces and specific surface structures compared to those formed in the absence of bacteria 56,58,59,[62][63][64] . Overall stone morphology is expected to be affected by the physical presence of bacteria within the stone matrix, but morphology also seems to be heavily influenced by the degree of pH change induced by bacteria.…”

“…Biomineralization influences biofilm architecture and properties by affecting its primary characteristics, including permeability and morphology, as well as detachment and transport processes within the biofilm 62,145,146 . Ureolytic biomineralization increases biofilm mechanical stability and decreases its susceptibility…”

“…Matrix of biopolymers comprised of extracellular polymeric substances (ePs) of microbial origin, in which biofilm microorganisms are embedded. to antimicrobials 62 . Under identical growth conditions, Li et al 146 characterized the biofilm formation of two types of P. mirabilis HI4320, urease-positive and urease-negative, and their response to exposure to the antibiotic ciprofloxacin.…”

Rutin, a Natural Inhibitor of IGPD Protein, Inhibits the Biofilm Formation inStaphylococcus xylosusATCC700404

“…What is more serious is that, S. xylosus has a strong ability to form biofilm [8,9]. Biofilms have been defined as multiplex networks consisting of a consortium of bacteria surrounded by a self-produced three-dimensional organic extracellular matrix [10][11][12][13][14][15] and bio-minerals [16,17]. The formation comprises a number of well-organized steps including attachment to a surface, formation of microcolonies, formation of young biofilm, development of differentiated structures in which individual bacteria as well as the entire community are surrounded by exopolysaccharides [14], and subsequent dispersal of mature biofilm [18].The dispersal of mature biofilms marks the completion of a full circle [19].…”

A matrix protein acts as a cue to preserve collective motility ofB. subtilisbiofilm cells

“…The ECM generates a physical connection between the biofilm cells like in higher multicellular organisms 2,16,17 . The main components of the bacterial ECM are: extracellular polysaccharides or exopolysaccharides, proteins, nucleic acids 15 , and biogenic minerals 18,19 .…”