A peptide of a type I toxin-antitoxin system induces morphological transformation from spiral shape to coccoids.

Toxin-antitoxin systems are found in many bacterial chromosomes and plasmids with roles ranging from plasmid stabilization to biofilm formation and persistence. In these systems, the expression/activity of the toxin is counteracted by an antitoxin, which, in type I systems, is an antisense RNA. While the regulatory mechanisms of these systems are mostly well defined, the toxins' biological activity and expression conditions are less understood.

The RNase J-Based RNA Degradosome Is Compartmentalized in the Gastric Pathogen Helicobacter pylori.

Posttranscriptional regulation is a major level of gene expression control in any cell. In bacteria, multiprotein machines called RNA degradosomes are central for RNA processing and degradation, and some were reported to be compartmentalized inside these organelleless cells. The minimal RNA degradosome of the important gastric pathogen is composed of the essential ribonuclease RNase J and RhpA, its sole DEAD box RNA helicase, and plays a major role in the regulation of mRNA decay and adaptation to gastric colonization.

The Sole DEAD-Box RNA Helicase of the Gastric Pathogen Is Essential for Colonization.

Present in every kingdom of life, generally in multiple copies, DEAD-box RNA helicases are specialized enzymes that unwind RNA secondary structures. They play major roles in mRNA decay, ribosome biogenesis, and adaptation to cold temperatures. Most bacteria have multiple DEAD-box helicases that present both specialized and partially redundant functions.

CozE is a member of the MreCD complex that directs cell elongation in Streptococcus pneumoniae.

Most bacterial cells are surrounded by a peptidoglycan cell wall that is essential for their integrity. The major synthases of this exoskeleton are called penicillin-binding proteins (PBPs). Surprisingly little is known about how cells control these enzymes, given their importance as drug targets.

Structural basis of host cell recognition by the pilus adhesin from Streptococcus pneumoniae.

Pili are fibrous virulence factors associated directly to the bacterial surface that play critical roles in adhesion and recognition of host cell receptors. The human pathogen Streptococcus pneumoniae carries a single pilus-related adhesin (RrgA) that is key for infection establishment and provides protection from bacterial challenge in animal infection models, but details of these roles remain unclear. Here we report the high-resolution crystal structure of RrgA, a 893-residue elongated macromolecule whose fold contains four domains presenting both eukaryotic and prokaryotic origins.

Stability and assembly of pilus subunits of Streptococcus pneumoniae.

Pili are surface-exposed virulence factors involved in bacterial adhesion to host cells. The Streptococcus pneumoniae pilus is composed of three structural proteins, RrgA, RrgB, and RrgC and three transpeptidase enzymes, sortases SrtC-1, SrtC-2, and SrtC-3. To gain insights into the mechanism of pilus formation we have exploited biochemical approaches using recombinant proteins expressed in Escherichia coli.

Sortase-mediated pilus fiber biogenesis in Streptococcus pneumoniae.

Streptococcus pneumoniae is a piliated pathogen whose ability to circumvent vaccination and antibiotic treatment strategies is a cause of mortality worldwide. Pili play important roles in pneumococcal infection, but little is known about their biogenesis mechanism or the relationship between components of the pilus-forming machinery, which includes the fiber pilin (RrgB), two minor pilins (RrgA, RrgC), and three sortases (SrtC-1, SrtC-2, SrtC-3). Here we show that SrtC-1 is the main pilus-polymerizing transpeptidase, and electron microscopy analyses of RrgB fibers reconstituted in vitro reveal that they structurally mimic the pneumococcal pilus backbone.