Bacillus anthracis chain length, a virulence determinant, is regulated by membrane localized serine/threonine protein kinase PrkC

Giving a signal: how protein phosphorylation helps Bacillus navigate through different life stages

Protein phosphorylation is a universal mechanism regulating a wide range of cellular responses across all domains of life. The antagonistic activities of kinases and phosphatases can orchestrate the life cycle of an organism. The availability of bacterial genome sequences, particularly Bacillus species, followed by proteomics and functional studies have aided in the identification of putative protein kinases and protein phosphatases, and their downstream substrates. Several studies have established the role of phosphorylation in different physiological states of Bacillus species as they pass through various life stages such as sporulation, germination, and biofilm formation. The most common phosphorylation sites in Bacillus proteins are histidine, aspartate, tyrosine, serine, threonine, and arginine residues. Protein phosphorylation can alter protein activity, structural conformation, and protein-protein interactions, ultimately affecting the downstream pathways. In this review, we summarize the knowledge available in the field of Bacillus signaling, with a focus on the role of protein phosphorylation in its physiological processes.

Recent advances in bacterial signaling by serine/threonine protein kinases

It has been nearly three decades since the discovery of the first bacterial serine/threonine protein kinase (STPK). Since then, a blend of technological advances has led to the characterization of a multitude of STPKs and phosphorylation substrates in several bacterial species that finely regulate intricate signaling cascades. Years of intense research from several laboratories have demonstrated unexpected roles for serine/threonine phosphorylation, regulating not only bacterial growth and cell division but also antibiotic persistence, virulence and infection, metabolism, chromosomal biology, and cellular differentiation. This review aims to provide an account of the most recent and significant developments in this up and growing field in microbiology.

Dynamics of Antibacterial Drone Establishment in Staphylococcus aureus: Unexpected Effects of Antibiotic Resistance Genes

The antibacterial drone (ABD) system is based on repurposing the phage-inducible staphylococcal pathogenicity islands (SaPIs) for use as antibacterial agents that are indifferent to antibiotic resistance. The ABDs were constructed by inserting tetM for tetracycline resistance (Tc^r) selection, replacing the SaPI virulence genes with bactericidal or bacteriostatic genes such as CRISPR/cas9/agrA, whose expression kills by double-strand cleavage of agrA, or CRISPR/dcas9/agrP₂P₃, whose expression blocks the target organism's virulence. ABD DNA is packaged in phage-like particles that attack their staphylococcal targets in vivo as well as in vitro. We determine ABD titers by transfer frequency, enumerate surviving cells as a function of multiplicity, and analyze the fate of ABD DNA with green fluorescent protein. An initial study revealed surprisingly that many more cells were killed by the ABD than were measured by transduction. Our study of this phenomenon has revealed several important features of the ABD system: (i) a significant number of entering ABD DNA molecules do not go on to establish stable transductants (i.e., are abortive); (ii) ABD cargo genes are expressed immediately following entry, even by the abortive ABDs; (iii) immediate plating on Tc-containing agar seriously underestimates particle numbers, partly owing to Tc inhibition of protein synthesis; (iv) replacement of tetM with cadA (conferring resistance to CdCl₂) provides more accurate particle enumeration; (v) ABDs expressing CRISPR/cas9/agrA kill ∼99.99% of infected cells and provide the most accurate measurement of particle numbers as well as proof of principle for the system; and (vi) surprisingly, TetM interferes with stable establishment of ABD DNA independently of Tc^r. IMPORTANCE For a particulate therapeutic agent, such as the ABD, accurate enumeration of particles is critical to enable evaluation of preparative procedures and calculation of therapeutic dosages. It is equally important that a selective marker used for these two purposes be biologically inert. We have long used tetM for these purposes but show here that tetM not only underestimates particle titers, by over 20-fold in some experiments, but also seriously impedes stable establishment of the therapeutic particle DNA. Given that tetM is a very convenient and widely used selective marker, publication of these findings is of considerable importance to the microbiological community as well as an interesting illustration of the unpredictable biological effects of genes taken out of their native context.