Antibacterial activity and mode of action of potassium tetraborate tetrahydrate against soft-rot bacterial plant pathogens

Unraveling the functional genes present in rhizosphere microbiomes of Solanum lycopersicum

The microbiomes living in the rhizosphere soil of the tomato plant contribute immensely to the state of health of the tomato plant alongside improving sustainable agriculture. With the aid of shotgun metagenomics sequencing, we characterized the putative functional genes (plant-growth-promoting and disease-resistant genes) produced by the microbial communities dwelling in the rhizosphere soil of healthy and powdery mildew-diseased tomato plants. The results identified twenty-one (21) plant growth promotion (PGP) genes in the microbiomes inhabiting the healthy rhizosphere (HR) which are more predomiant as compared to diseased rhizosphere (DR) that has nine (9) genes and four (4) genes in bulk soil (BR). Likewise, we identified some disease-resistant genes which include nucleotide binding genes and antimicrobial genes. Our study revealed fifteen (15) genes in HR which made it greater in comparison to DR that has three (3) genes and three (3) genes in bulk soil. Further studies should be conducted by isolating these microorganisms and introduce them to field experiments for cultivation of tomatoes.

Genomic Distribution of Pro-Virulent cpdB-like Genes in Eubacteria and Comparison of the Enzyme Specificity of CpdB-like Proteins from Salmonella enterica, Escherichia coli and Streptococcus suis

The cpdB gene is pro-virulent in avian pathogenic Escherichia coli and in Salmonella enterica, where it encodes a periplasmic protein named CpdB. It is structurally related to cell wall-anchored proteins, CdnP and SntA, encoded by the also pro-virulent cdnP and sntA genes of Streptococcus agalactiae and Streptococcus suis, respectively. CdnP and SntA effects are due to extrabacterial hydrolysis of cyclic-di-AMP, and to complement action interference. The mechanism of CpdB pro-virulence is unknown, although the protein from non-pathogenic E. coli hydrolyzes cyclic dinucleotides. Considering that the pro-virulence of streptococcal CpdB-like proteins is mediated by c-di-AMP hydrolysis, S. enterica CpdB activity was tested as a phosphohydrolase of 3'-nucleotides, 2',3'-cyclic mononucleotides, linear and cyclic dinucleotides, and cyclic tetra- and hexanucleotides. The results help to understand cpdB pro-virulence in S. enterica and are compared with E. coli CpdB and S. suis SntA, including the activity of the latter on cyclic-tetra- and hexanucleotides reported here for the first time. On the other hand, since CpdB-like proteins are relevant to host-pathogen interactions, the presence of cpdB-like genes was probed in eubacterial taxa by TblastN analysis. The non-homogeneous genomic distribution revealed taxa with cpdB-like genes present or absent, identifying eubacteria and plasmids where they can be relevant.