Role of Phenotypic Switching in Stability and Persistence of Pseudomonas aeruginosa Biofilms

Mirani

et al. 2022

Cells

Self Cite

The present study discusses a biofilm-positive P. aeruginosa isolate that survives at pH levels ranging from 4.0 to 9.0. The biofilm consortia were colonized with different phenotypes i.e., planktonic, slow-growing and metabolically inactive small colony variants (SCVs). The lower base of the consortia was occupied by SCVs. These cells were strongly attached to solid surfaces and interconnected through a network of nanotubes. Nanotubes were observed at the stationary phase of biofilm indwellers and were more prominent after applying weight to the consortia. The scanning electron micrographs indicated that the nanotubes are polar appendages with intraspecies connectivity. The micrographs indicated variations in physical dimensions (length, width, and height) and a considerable reduction in volume due to weight pressure. A total of 35 cells were randomly selected. The mean volume of cells before the application of weight was 0.288µm3, which was reduced to 0.144 µm3 after the application of weight. It was observed that a single cell may produce as many as six nanotubes, connected simultaneously to six neighbouring cells in different directions. The in-depth analysis confirmed that these structures were the intra-species connecting tools as no free nanotubes were found. Furthermore, after the application of weight, cells incapable of producing nanotubes were wiped out and the surface was covered by nanotube producers. This suggests that the nanotubes give a selective advantage to the cells to resist harsh environmental conditions and weight pressure. After the removal of weight and proper supply of nutrients, these phenotypes reverted to normal planktonic lifestyles. It is concluded that the nanotubes are not merely the phenomenon of dying cells; rather they are a connectivity tool which helps connected cells to tolerate and resist environmental stress.

Section: Resultssupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Nanotubes Formation in P. aeruginosa

Mirani

et al. 2022

Cells

Self Cite

Postępy Mikrobiologii - Advancements of Microbiology

“…Badania przeprowadzone przez Mirani i wsp. [29] wykazały, że SCV P. aeruginosa mają znaczenie w utrzymaniu trwałości i stabilności biofilmu, a nie w początkowych etapach jego tworzenia -tu główną rolę autorzy przypisują populacji typu dzikiego. W miarę dojrzewania biofilmu pojawiają się formy SCV i zaczynają dominować co może sugerować, że populacja SCV jest "produktem" środowiska biofilmu.…”

Section: Small Colony Variants -Przyczyna Zakażeń Przewlekłychunclassified

“…W miarę dojrzewania biofilmu pojawiają się formy SCV i zaczynają dominować co może sugerować, że populacja SCV jest "produktem" środowiska biofilmu. Wykazano również, że SCV w biofilmie charakteryzowały się znaczną chropowatością powierzchni, zwiększonymi właściwościami hydrofobowymi komórek i tym samym zwiększoną zdolnością do adhezji i kolonizacji [29].…”

Section: Small Colony Variants -Przyczyna Zakażeń Przewlekłychunclassified

Small Colony Variants – The Cause Of Chronic Infections

Nowicka

Piątkowska

2021

Some microorganisms are characterised by the ability to create specific morphological varieties called Small Colony Variants (SCVs). This characteristic was noted, among others, in Gram-positive cocci, mainly staphylococci, but also in Gram-negative bacilli. The properties of Small Colony Variants that differentiate them from wild-type colonies (mainly their small size) facilitate their intracellular survival (e.g. in epithelial or endothelial cells) as a result of which they can escape host immune response. In this way, SCV forms avoid the effects of complement components or antibodies. They are also characterised by resistance to antibiotics, mainly aminoglycoside or combination drugs, such as trimethoprim-sulfamethoxazole. The above features, which are important from a clinical point of view, namely small size and antibiotic resistance, make SCV one of the main causes of chronic, latent and recurrent infections which are difficult not only to diagnose, but also to treat. According to the literature, SCV of various microorganisms can be isolated from systemic infections of various organs and therefore from different clinical materials (e.g. blood, bones, soft tissues). SCV forms of Staphylococcus aureus are often isolated from patients with cystic fibrosis or osteomyelitis. The paper presents the characteristics and clinical relevance of this unique morphological form of bacteria. 1. General characteristics of SCV. 2. Formation mechanism of SCV. 3. Avoidance of host immunity by Small Colony Variants. 4. Clinical significance of SCV -description of selected cases. 4.1. Staphylococci. 4.2. Pseudomonas aeruginosa. 4.3. SCVs of other micro organisms.

Forms of Bacterial Survival in Model Biofilms

et al. 2022

Bacterial survival upon sharp fluctuations of environmental parameters and exposure to lethal doses of stressors (antibiotics, disinfectants, heat shock, and others) is ensured by the use of different strategies of resistance, an important place among which is occupied by the forms with reduced or stopped metabolism, antibiotic tolerant (AT) persister (P) cells, anabiotic dormant forms (DFs), and viable but non-culturable (VBNC) cells. Elucidating the role of these forms of bacterial resistance to an impact of chemical and biological toxicants and physical stressors is of great fundamental and practical interest. The aim of this research was to study the dynamics of the resistance forms in bacteria developing in biofilms and, for comparison in liquid media, upon exposure to lethal doses of antibiotics and heat shock (80 °C, 15 min). In the trials, the experimental model of the development of monospecies and binary forms of bacterial biofilms including contaminants of meat products (eight strains of genera Pseudomonas, Escherichia, Salmonella, Staphylococcus, and Kocuria) on the fiberglass filters was used. It was established that survival of populations in the presence of lethal doses of antibiotics and upon heating was ensured by persister cells forming in bacterial populations and, at the late stages of the development of biofilm or planktonic cultures (28 days of incubation), by anabiotic DFs. With that, the number of thermoresistant (TR) DFs (103–104 CFU/mL) in dying biofilms (28 days) developing in the standard conditions (composition and volume of a medium, pH, growth temperature) weakly depended on the bacterial taxonomic status. This study demonstrates the heterogeneity of DF populations of biofilm bacterial cultures in terms of the depth of dormancy, as a result of which the number of thermoresistant DFs after heating can exceed their total number before heating (due to the effect of DF revival, resuscitation). When studying the dynamics of TR cells and P cells in bacterial biofilm and planktonic cultures, it was found that their number (CFU/mL) in populations decreased up to the absence of TR cells and P cells on the 21st day of growth and was restored on the 28th day of growth. The revealed phenomenon can be explained only by cardinal changes in the ultrastructural organization of cells, namely, cytoplasm vitrification due to a sharp decrease in an amount of free water in a cell, which, according to the results obtained, occurs in the period between the 21st and 28th days of incubation. A high degree of correlation between the number of AT cells and TR cells (0.5–0.92) confirms the hypothesis that regards P cells as precursors of DFs.