Biology subjects

Amarnath, K.

Publications and source records attributed to Amarnath, K..

3 recordsLinked to original sources

bioRxiv2022

A Genome-Scale Metabolic Model of Marine Heterotroph Vibrio splendidus sp. 1A01

While the Vibrio splendidus species is best known as an opportunistic pathogen in oysters, the Vibrio splendidus sp. 1A01 strain was first identified as an early colonizer of synthetic chitin particles incubated in seawater. To gain a better understanding of its metabolism, a genome-scale metabolic model (GSMM) of V. splendidus sp. 1A01 was reconstructed. GSMMs enable us to simulate all metabolic reactions in a bacterial cell using Flux Balance Analysis. A draft model was built using an automated pipeline from BioCyc. Manual curation was then performed based on experimental data, in part by gap-filling metabolic pathways and tailoring the models biomass reaction to V. splendidus sp. 1A01. The challenges of building a metabolic model for a marine microorganism like V. splendidus sp. 1A01 are described.

microbiology↗

bioRxiv2021

Stress-induced cross-feeding of internal metabolites provides a dynamic mechanism of microbial cooperation

Metabolic cross-feeding plays vital roles in promoting ecological diversity. While some microbes depend on exchanges of essential nutrients for growth, forces driving the extensive cross-feeding needed to support the coexistence of free-living microbes are poorly understood. Here we characterize bacterial physiology under self-acidification, and establish that extensive excretion of key metabolites following acidification provides a collaborative, inter-species mechanism of stress resistance. This collaboration occurs not only between species isolated from the same community, but also between unrelated species with complementary (glycolytic vs. gluconeogenic) modes of metabolism. Cultures of such communities cycle through different phases in growth-dilution experiments, comprising of exponential growth, growth arrest upon acidification, collaborative stress relief, and growth recovery, with each phase involving distinct physiological states of individual species. Our findings challenge the static view of ecosystems commonly portrayed in ecological models, and offer an alternative dynamical view based on growth advantages of different species in different phases.

microbiology↗

bioRxiv2017

Natural changes in light interact with circadian regulation at promoters to control gene expression in cyanobacteria

The circadian clock interacts with other regulatory pathways to tune physiology to predictable daily changes and unexpected environmental fluctuations. However, the complexity of circadian clocks in higher organisms has prevented a clear understanding of how natural environmental conditions affect circadian clocks and their physiological outputs. Here, we dissect the interaction between circadian regulation and responses to fluctuating light in the cyanobacterium Synechococcus elongatus. We demonstrate that natural changes in light intensity substantially affect the expression of hundreds of circadian-clock-controlled genes, many of which are involved in key steps in metabolism. These changes in expression arise from control of RNA polymerase recruitment to promoters by circadian and light-responsive regulation of a network of transcription factors including RpaA and RpaB. Using phenomenological modeling constrained by our data, we reveal simple principles that underlie the small number of stereotyped responses of dusk circadian genes to changes in light.

bioinformatics↗