Contribution of Cell Elongation to the Biofilm Formation of Pseudomonas aeruginosa during Anaerobic Respiration

Abstract

Pseudomonas aeruginosa, a gram-negative bacterium of clinical importance, forms more robust biofilm during anaerobic respiration, a mode of growth presumed to occur in abnormally thickened mucus layer lining the cystic fibrosis (CF) patient airway. However, molecular basis behind this anaerobiosis-triggered robust biofilm formation is not clearly defined yet. Here, we identified a morphological change naturally accompanied by anaerobic respiration in P. aeruginosa and investigated its effect on the biofilm formation in vitro. A standard laboratory strain, PAO1 was highly elongated during anaerobic respiration compared with bacteria grown aerobically. Microscopic analysis demonstrated that cell elongation likely occurred as a consequence of defective cell division. Cell elongation was dependent on the presence of nitrite reductase (NIR) that reduces nitrite (NO2 −) to nitric oxide (NO) and was repressed in PAO1 in the presence of carboxy-PTIO, a NO antagonist, demonstrating that cell elongation involves a process to respond to NO, a spontaneous byproduct of the anaerobic respiration. Importantly, the non-elongated NIR-deficient mutant failed to form biofilm, while a mutant of nitrate reductase (NAR) and wild type PAO1, both of which were highly elongated, formed robust biofilm. Taken together, our data reveal a role of previously undescribed cell biological event in P. aeruginosa biofilm formation and suggest NIR as a key player involved in such process.

cbb 3 -Type Cytochrome c Oxidases, Aerobic Respiratory Enzymes, Impact the Anaerobic Life of Pseudomonas aeruginosa PAO1

“…1B), suggesting that these respiratory enzymes have a physiological role under anoxic denitrifying conditions. In a study by Yoon et al, it was demonstrated that P. aeruginosa PAO1 elongates and aggregates in anoxic planktonic shaking cultures (26). Similar phenomena were observed in the WT by DIC observation.…”

“…Under anoxic conditions where NO 3 Ϫ is present, P. aeruginosa can grow through denitrification, in which NO 3 Ϫ is reduced subsequently to NO 2 Ϫ , NO, N 2 O, and, finally, to N 2 (3). Cell elongation under anoxic conditions is attributed to the accumulation of NO that is produced during such a process (26). Our data showed that cbb 3 oxidases affect cell morphology; hence, the effect of cbb 3 oxidases on the denitrification process was investigated.…”

Anaerobiosis-Induced Loss of Cytotoxicity Is Due to Inactivation of Quorum Sensing in Pseudomonas aeruginosa

“…P. aeruginosa laboratory strains (PAO1, PA14, PAK, and FRD1) and pneumonia patient isolates have been previously described (25,47,57,58). The PAO1 ⌬lasB mutant was purchased from a P. aeruginosa transposon mutant library (www.genome.washington.edu /UWGC/pseudomonas) and sequence verified.…”

Plasticity of Candida albicans Biofilms

“…As the biofilm evolves, it undergoes cellular differentiation and multicellular morphogenesis. In select bacteria, there is stratification of cellular phenotypes and the development of an often complex multicellular architecture (110)(111)(112)(113). In Pseudomonas aeruginosa, cells differentiate from a round to an elongated phenotype (113), and they exhibit changes in physiology, gene transcription, and protein synthesis (81,(114)(115)(116).…”

“…In select bacteria, there is stratification of cellular phenotypes and the development of an often complex multicellular architecture (110)(111)(112)(113). In Pseudomonas aeruginosa, cells differentiate from a round to an elongated phenotype (113), and they exhibit changes in physiology, gene transcription, and protein synthesis (81,(114)(115)(116). One of the most dramatic phenotypic transitions is that of E. coli (80,86) and P. aeruginosa (81,117,118).…”