A C-terminal truncated mutation of licC attenuates the virulence of Streptococcus pneumoniae

Glucose levels affect MgaSpn regulation on the virulence and adaptability of Streptococcus pneumoniae

Streptococcus pneumoniae can regulate virulence gene expression by sensing environmental changes, which is key to its pathogenicity. The global transcription regulator MgaSpn of Streptococcus pneumoniae regulates virulence genes expression by directly binding to the promoter regions, but its role in response to different environments remains unclear. In this study, we found that glucose levels could affect phosphocholine content, which was mediated by MgaSpn. MgaSpn can also alter its anti-phagocytosis ability, depending on the availability of glucose. In addition, transcriptome analysis of wild-type D39s in low and high glucose concentrations revealed that MgaSpn was also involved in the regulation of carbon metabolism inhibition (carbon catabolite repression; CCR) and translation processes, which made S. pneumoniae highly competitive in fluctuating environments. In conclusion, MgaSpn is closely related to the virulence and environmental adaptability of Streptococcus pneumoniae.

The predominance of nucleotidyl activation in bacterial phosphonate biosynthesis

Phosphonates are rare and unusually bioactive natural products. However, most bacterial phosphonate biosynthetic capacity is dedicated to tailoring cell surfaces with molecules like 2-aminoethylphosphonate (AEP). Although phosphoenolpyruvate mutase (Ppm)-catalyzed installation of C-P bonds is known, subsequent phosphonyl tailoring (Pnt) pathway steps remain enigmatic. Here we identify nucleotidyltransferases in over two-thirds of phosphonate biosynthetic gene clusters, including direct fusions to ~60% of Ppm enzymes. We characterize two putative phosphonyl tailoring cytidylyltransferases (PntCs) that prefer AEP over phosphocholine (P-Cho) – a similar substrate used by the related enzyme LicC, which is a virulence factor in Streptococcus pneumoniae. PntC structural analyses reveal steric discrimination against phosphocholine. These findings highlight nucleotidyl activation as a predominant chemical logic in phosphonate biosynthesis and set the stage for probing diverse phosphonyl tailoring pathways.

Phosphonate modifications can be present on microbial cell surfaces. Here the authors perform bioinformatics analyses and observe a widespread occurrence of nucleotidyltransferase-encoding genes in bacterial phosphonate biosynthesis and functionally characterize two of the identified phosphonate specific cytidylyltransferases (PntCs) and determine the crystal structure of T. denticola PntC.

Giardia's primitive GPL biosynthesis pathways with parasitic adaptation 'patches': implications for Giardia's evolutionary history and for finding targets against Giardiasis

Giardia is a worldwide spread protozoan parasite colonizing in small intestines of vertebrates, causing Giardiasis. The controversy about whether it is an extremely primitive eukaryote or just a highly evolved parasite has become a fetter to its uses as a model for both evolutionary and parasitological studies for years. Glycerophospholipid (GPL) synthesis is a conserved essential cellular process, and thus may retain some original features reflecting its evolutionary position, and this process should also have undergone parasitic adaptation to suit Giardia’s dietary lipid-rich environment. Thus, GPL synthesis pathways may be a perfect object to examine the controversy over Giardia. Here, we first clarified Giardia’s previously confusing GPL synthesis by re-identifying a reliable set of GPL synthesis genes/enzymes. Then using phylogenetic and comparative genomic analyses, we revealed that these pathways turn out to be evolutionarily primitive ones, but with many secondary parasitic adaptation ‘patches’ including gene loss, rapid evolution, product relocation, and horizontal gene transfer. Therefore, modern Giardia should be a mosaic of ‘primary primitivity’ and ‘secondary parasitic adaptability’, and to make a distinction between the two categories of features would restart the studies of eukaryotic evolution and parasitic adaptation using Giardia as a model system.