Genome-scale fitness profile of Caulobacter crescentus grown in natural freshwater.

Bacterial genomes evolve in complex ecosystems and are best understood in this natural context, but replicating such conditions in the lab is challenging. We used transposon sequencing to define the fitness consequences of gene disruption in the bacterium Caulobacter crescentus grown in natural freshwater, compared with axenic growth in common laboratory media. Gene disruptions in amino-acid and nucleotide sugar biosynthesis pathways and in metabolic substrate transport machinery impaired fitness in both lake water and defined minimal medium relative to complex peptone broth.

Biological and Chemical Adaptation to Endogenous Hydrogen Peroxide Production in D39.

The catalase-negative, facultative anaerobe D39 is naturally resistant to hydrogen peroxide (HO) produced endogenously by pyruvate oxidase (SpxB). Here, we investigate the adaptive response to endogenously produced HO. We show that lactate oxidase, which converts lactate to pyruvate, positively impacts pyruvate flux through SpxB and that mutants produce significantly lower HO.

Phosphinothricin Acetyltransferases Identified Using In Vivo, In Vitro, and Bioinformatic Analyses.

Acetylation of small molecules is widespread in nature, and in some cases, cells use this process to detoxify harmful chemicals. Streptomyces species utilize a Gcn5 N-acetyltransferase (GNAT), known as Bar, to acetylate and detoxify a self-produced toxin, phosphinothricin (PPT), a glutamate analogue. Bar homologues, such as MddA from Salmonella enterica, acetylate methionine analogues such as methionine sulfoximine (MSX) and methionine sulfone (MSO), but not PPT, even though Bar homologues are annotated as PPT acetyltransferases.

Complex regulation of the sirtuin-dependent reversible lysine acetylation system of .

The extensive involvement of the reversible lysine acylation (RLA) system in metabolism has attracted the attention of investigators interested in understanding the fundamentals of prokaryotic and eukaryotic cell function. Research in this area of cell physiology is diverse, ranging from probing the molecular bases of human diseases, to optimizing engineered metabolic pathways for biotechnological applications, to advancing our understanding of fundamental cellular processes, among others. A gap of knowledge exists in our understanding of the regulatory circuitry that integrates the expression of genes encoding modifiers (, acyltransferases) and demodifiers (, deacylases) with the expression of genes encoding known targets of the system.

Deciphering the Regulatory Circuitry That Controls Reversible Lysine Acetylation in Salmonella enterica.

Unlabelled: In Salmonella enterica, the reversible lysine acetylation (RLA) system is comprised of the protein acetyltransferase (Pat) and sirtuin deacetylase (CobB). RLA controls the activities of many proteins, including the acetyl coenzyme A (acetyl-CoA) synthetase (Acs), by modulating the degree of Acs acetylation. We report that IolR, a myo-inositol catabolism repressor, activates the expression of genes encoding components of the RLA system.

Acylation of Biomolecules in Prokaryotes: a Widespread Strategy for the Control of Biological Function and Metabolic Stress.

Acylation of biomolecules (e.g., proteins and small molecules) is a process that occurs in cells of all domains of life and has emerged as a critical mechanism for the control of many aspects of cellular physiology, including chromatin maintenance, transcriptional regulation, primary metabolism, cell structure, and likely other cellular processes.

In Salmonella enterica, the Gcn5-related acetyltransferase MddA (formerly YncA) acetylates methionine sulfoximine and methionine sulfone, blocking their toxic effects.

Protein and small-molecule acylation reactions are widespread in nature. Many of the enzymes catalyzing acylation reactions belong to the Gcn5-related N-acetyltransferase (GNAT; PF00583) family, named after the yeast Gcn5 protein. The genome of Salmonella enterica serovar Typhimurium LT2 encodes 26 GNATs, 11 of which have no known physiological role.

Instability of ackA (acetate kinase) mutations and their effects on acetyl phosphate and ATP amounts in Streptococcus pneumoniae D39.

Acetyl phosphate (AcP) is a small-molecule metabolite that can act as a phosphoryl group donor for response regulators of two-component systems (TCSs). The serious human respiratory pathogen Streptococcus pneumoniae (pneumococcus) synthesizes AcP by the conventional pathway involving phosphotransacetylase and acetate kinase, encoded by pta and ackA, respectively. In addition, pneumococcus synthesizes copious amounts of AcP and hydrogen peroxide (H(2)O(2)) by pyruvate oxidase, which is encoded by spxB.