Morphological plasticity of bacteria—Open questions

Abstract

Morphological plasticity of bacteria is a cryptic phenomenon, by which bacteria acquire adaptive benefits for coping with changing environments. Some environmental cues were identified to induce morphological plasticity, but the underlying molecular mechanisms remain largely unknown. Physical and chemical factors causing morphological changes in bacteria have been investigated and mostly associated with potential pathways linked to the cell wall synthetic machinery. These include starvation, oxidative stresses, predation effectors, antimicrobial agents, temperature stresses, osmotic shock, and mechanical constraints. In an extreme scenario of morphological plasticity, bacteria can be induced to be shapeshifters when the cell walls are defective or deficient. They follow distinct developmental pathways and transform into assorted morphological variants, and most of them would eventually revert to typical cell morphology. It is suggested that phenotypic heterogeneity might play a functional role in the development of morphological diversity and/or plasticity within an isogenic population. Accordingly, phenotypic heterogeneity and inherited morphological plasticity are found to be survival strategies adopted by bacteria in response to environmental stresses. Here, microfluidic and nanofabrication technology is considered to provide versatile solutions to induce morphological plasticity, sort and isolate morphological variants, and perform single-cell analysis including transcriptional and epigenetic profiling. Questions such as how morphogenesis network is modulated or rewired (if epigenetic controls of cell morphogenesis apply) to induce bacterial morphological plasticity could be resolved with the aid of micro-nanofluidic platforms and optimization algorithms, such as feedback system control.

Marine Bacteria Display Different Escape Mechanisms When Facing Their Protozoan Predators

“…It is therefore possible that bacteria are able to shape filaments induced by protists by-products as a defense mechanism to avoid amoeba phagocytosis, which would up-take only the smaller bacteria as described previously [ 70 ]. Morphological plasticity as part of phenotypic heterogeneity has been poorly studied while it may play a functional role within isogenic bacterial populations (reviewed in [ 71 ]). Filamentous morphology is known to provide survival advantages in particular during environmental stress or the presence of antibiotics or predators (reviewed in [ 72 ]).…”

Can Halophilic and Psychrophilic Microorganisms Modify the Freezing/Melting Curve of Cold Salty Solutions? Implications for Mars Habitability

“…We cannot exclude the possibility of an overestimation of the survivability of E. coli due to these changes in morphology that differed from the normal shape of cells in the control culture and used to establish the cytometry settings for measures; and even the yellow color of these more spherical cells, which indicates an intermediate stage on the path to death, could have contributed to this overestimation. Several reports have shown that bacterial morphological changes are indeed caused by environmental stress conditions (Shen and Chou, 2016 ), which happens especially in salty media and at low temperatures for gram-negative bacteria such as E. coli (Yang et al , 2016 ). In particular, different types of bacteria tolerant to high perchlorate concentrations became larger and morphologically aberrant (Oren et al , 2014 ), or aggregated into long cellular chains (Beblo-Vranesevic et al , 2017 ), when exposed to this salt.…”

Growth and Metabolism of Lacticaseibacillus casei and Lactobacillus kefiri Isolated from Qymyz, a Traditional Fermented Central Asian Beverage

“…The microscopic analysis of the coagulated media revealed a shortening of rods, which, according to [33], is characteristic of L. kefiri, as it has the ability to form short rods (3 nm) or long filaments (15 nm). Morphological change could affect the metabolism of L. kefiri and explain its biphasic growth [36]. Rajoka et al [37] found that L. kefiri is able to attach to the grain surface in Brazilian kefir and is important for the production of the kefiran polymer present in the kefir grain's structure, which could explain the coagulation of the media.…”