Biology subjects

Kale, T.

Publications and source records attributed to Kale, T..

4 recordsLinked to original sources

bioRxiv2024

Mechanics of E. coli cell width homeostasis and bulging dynamics from MreB and septum inhibition

The mechanobiology of cytoskeleton and cell envelope play a vital role in cell shape homeostasis. In the gram-negative model rod-shaped bacterium Escherichia coli antibiotics that weaken the cell envelope are seen to result in bulges that eventually lead to lysis. Here, we quantify the shape dynamics of E. coli treated with cephalexin, a PBP3 inhibitor and A22, an MreB polymerization inhibitor from single cell microscopy. We find low concentrations of both inhibitors result in bulge formation with multiple cell shapes observed: rugby, large bacilli and rods with two and three bulges. We quantify the parameters of cell envelope rigidity, pressure and fluidity obtained from fitting a computational model of shell-mechanics to length and width dynamics from experiment. Using this optimized model we estimate the turgor and growth pressures of untreated growing cells as {approx}0.15 MPa and {approx}0.4 MPa. The bulge expansion dynamics correlate most prominently with a change in bending rigidity of the cell wall and cytoskeleton. Simulations predict a threshold behavior in response to envelope bending rigidity that is validated by comparison with experiments of E. coli treated with A22 either in isolation or in combination, resulting in loss of width control and cell shape change.

cell biology↗

bioRxiv2024

Reducing phytate, an antinutritional factor, in sorghum dough using phytase-expressing Saccharomyces cerevisiae

Phytate, a major antinutritional factor present in millets and legumes, chelates minerals like calcium, iron and zinc leading to their poor bioavailability. Phytase from Aspergillus japonicus was expressed extracellularly in Saccharomyces cerevisiae and its ability to reduce phytate in sorghum flour was determined. When the A. japonicus phytase-expressing strain was used to ferment sorghum dough, phytate reduction increased by 43% as compared to control strain. This approach of simultaneous proofing and phytate reduction can be used to increase micronutrient availability of non-wheat food products.

biochemistry↗

bioRxiv2022

Effect of Size Variability, Filamentation and Division Dynamics on Escherichia coli Allometry

The cell surface area (SA) increase with volume (V) for cells is determined by growth and regulation of size and shape. Most studies of the rod-shaped model bacterium Escherichia coli have focussed on the phenomenology or molecular mechanisms governing such scaling. Here, we proceed to examine the role of population statistics and cell division dynamics in such scaling by a combination of microscopy, image analysis and statistical simulations. We find that while cells sampled from mid-log cultures follow a 2/3 exponent, similar to geometric (Platonic) solids, drug induced filamentous cells have higher exponent values. Modulating the growth rate to change the proportion of filamentous cells, we find SA-V scales with an exponent > 2/3, exceeding that predicted by the geometric scaling law. However, since increasing growth rates alter the mean and spread of population cell size distributions, we use statistical modeling to disambiguate between the effect of the mean size and variability. Simulating (i) increasing mean cell length with a constant standard deviation (s.d.) and (ii) a constant mean length with increasing s.d. results in scaling exponents that exceed the 2/3 geometric law, when population variability is included. In order to overcome possible effects of statistical sampling of unsynchronized cell populations, we virtually synchronized the estimation of SA-V scaling from single cell growth experiments. We find the exponent depends on the stage with the maximal cell length heterogeneity and scaling exponent observed during the intermediate period between birth (B) and division (D) stages. These results point to a need to consider population statistics and a role for cell growth and division when estimating SA-V scaling of bacterial cells.

biophysics↗

bioRxiv2022

Cell size and shape regulation of E. coli determines surface area scaling with volume

The scaling of surface area and volume of cells has widespread consequences for cell physiology, growth and adaptation. While the surface area increases with volume as SA ~ V{gamma} the scaling exponent for proportional growth maintaining the shape and aspect is {gamma} ~ 2/3 or 0.66. However most well-studied cellular systems deviate from this standard exponent. At the same time, a mechanism that could predict the biological or physical basis of these scaling relations remains unclear. Here, we quantify the surface area scaling with volume of Escherichia coli cells with varying growth rates and under different conditions and find the scaling exponent varies from {gamma} ~ 0.7 to 0.9. A model of uncorrelated statistical variation of cell lengths and widths can reproduce the exponent observed in experiment. Average values of length and width on the other hand results in an impression of ideal geometric scaling, as reported in some studies. Experimental data however suggests that E. coli cell width is strongly correlated with length and a model of saturation best explains the observations. We hypothesize this model of cell size and shape regulation could serve the function of optimizing flux of nutrients, within the constraints of the cell division machinery.

microbiology↗