Mycobacterial Populations Partly Change the Proportions of the Cells Undergoing Asymmetric/Symmetric Divisions in Response to Glycerol Levels in Growth Medium

Abstract

Twenty to thirty percent of the septating mycobacterial cells of the mid-log phase population showed highly deviated asymmetric constriction during division (ACD), while the remaining underwent symmetric constriction during division (SCD). The ACD produced short-sized cells (SCs) and normal/long-sized cells (NCs) as the sister–daughter cells, but with significant differential susceptibility to antibiotic/oxidative/nitrite stress. Here we report that, at 0.2% glycerol, formulated in the Middlebrook 7H9 medium, a significantly high proportion of the cells were divided by SCD. When the glycerol concentration decreased to 0.1% due to cell-growth/division, the ACD proportion gradually increased until the ACD:SCD ratio reached ~50:50. With further decrease in the glycerol levels, the SCD proportion increased with concomitant decrease in the ACD proportion. Maintenance of glycerol at 0.1%, through replenishment, held the ACD:SCD proportion at ~50:50. Transfer of the cells from one culture with a specific glycerol level to the supernatant from another culture, with a different glycerol level, made the cells change the ACD:SCD proportion to that of the culture from which the supernatant was taken. RT-qPCR data showed the possibility of diadenosine tetraphosphate phosphorylase (MSMEG_2932), phosphatidylinositol synthase (MSMEG_2933), and a Nudix family hydrolase (MSMEG_2936) involved in the ACD:SCD proportion-change in response to glycerol levels. We also discussed its physiological significance.

Clinically encountered growth phenotypes of tuberculosis-causing bacilli and their in vitro study: A review

“…Another source of heterogeneity on the single cell level is that mycobacteria grow and divide asymmetrically ( Aldridge et al., 2012 ) ( Joyce et al., 2012 ; Vijay et al., 2012 ; Vijay et al., 2014a ; Vijay et al., 2014b ; Rego et al., 2017 ; Priestman et al., 2017 ; Logsdon and Aldridge, 2018 ; Ufimtseva et al., 2019 ). The resultant cell size variability has been observed in in vitro models as well as in clinical samples ( Vijay et al., 2017b ; Ufimtseva et al., 2019 ; Pradhan et al., 2021 ). Differences in cell size yield differential susceptibilities to host and antibiotic stresses, which can in turn affect their survival and culturability ( Richardson et al., 2016 ; Vijay et al., 2017a ; Vijay et al., 2017b ).…”