Bacillus cereuscell and spore properties as influenced by the micro-structure of the medium

Abstract

Aim: To investigate the effect of different growth conditions on Bacillus cereus cell and spore properties. Methods and Results: Bacillus cereus was grown on agar plates with different surface water conditions (wet and dry) or viscosity. Cell populations displayed different types of behaviour, and heterogeneity was manifested in cell motility and dimension. Spore populations were heterogeneous regarding their properties, namely size and thermal resistance. The smallest spores were produced from flagellated cells, which also displayed jet‐motility, growing on the wettest agar. Cytometric analysis also revealed within the smallest spores a sub‐population labelled by propidium iodide (PI), indicating that spore populations were partly damaged. Nonmotile cells grown on diffusion‐limiting media were elongated and produced the least thermal‐resistant spores. Conclusions: The micro‐structural properties of the media were found to influence cell and spore properties. Abundant surface water enabled flagellar motility and resulted in a heterogeneous cell and spore population, the latter including small and damaged spores. High viscosity gave rise to filamentous cells and more heat‐sensitive spores. Significance and Impact of the Study: This study provides useful information on conditions resulting in heterogeneous populations of damaged and heat‐sensitive spores.

Applications of Flow Cytometry to Characterize Bacterial Physiological Responses

“…In a different bacterium, Stecchini et al [8] investigated the effects of changes in humidity and viscosity in growth cultures of B. cereus , a human pathogen [77] over cell motility, spore dimension, and thermal resistance. Such parameters were measured by forward and side scattering (assess dimension) and propidium iodide (thermal damage) [8].…”

“…Such parameters were measured by forward and side scattering (assess dimension) and propidium iodide (thermal damage) [8]. …”

“…For instance, when the subpopulation produces and secretes an inhibitor, a growth factor, or an autoinducer into the medium, it causes a response from the rest of the cells [6]. The origins of such heterogeneity are, according to the literature [7], due to differences in microenvironments [8], created by a large number of bacterial cells growing in and modifying a culture, giving rise to what is called extrinsic noise, in combination with intrinsic cellular noise, due to the fact that each cell possess a different spatiotemporal distribution of cellular components, that is, the threshold levels of molecules that switch on/off gene expression arose at different times in each cell, since gene expression is stochastic [9]. …”

High pressure inactivation ofClostridium botulinumtype E endospores in model emulsion systems

“…This could be explained by the heterogeneity of bacterial spore populations. [34][35][36][37][38][39] The relatively low hydrophobicity and distribution between boundary and water phase of C. botulinum type E spores observed here might be due to such variations. Additionally, C. botulinum type E is known to possess a large exosporium.…”

Flow cytometry for bacteria: enabling metabolic engineering, synthetic biology and the elucidation of complex phenotypes

“…[7 , 64,65] Gram staining -Hexidium iodine (Gram À impermeable) -Oregon green (with germ agglutinin) stains Gram + -Discriminate mixed populations of Gram + and Gram À cells.…”