Genomic adaptation of Pseudomonas strains to acidity and antibiotics in hydrothermal vents at Kolumbo submarine volcano, Greece.

Although the rise of antibiotic and multidrug resistant bacteria is one of the biggest current threats to human health, our understanding of the mechanisms involved in antibiotic resistance selection remains scarce. We performed whole genome sequencing of 21 Pseudomonas strains, previously isolated from an active submarine volcano of Greece, the Kolumbo volcano. Our goal was to identify the genetic basis of the enhanced co-tolerance to antibiotics and acidity of these Pseudomonas strains. Pangenome analysis identified 10,908 Gene Clusters (GCs). It revealed that the numbers of phage-related GCs and sigma factors, which both provide the mechanisms of adaptation to environmental stressors, were much higher in the high tolerant Pseudomonas strains compared to the rest ones. All identified GCs of these strains were associated with antimicrobial and multidrug resistance. The present study provides strong evidence that the CO2-rich seawater of the volcano associated with low pH might be a reservoir of microorganisms carrying multidrug efflux-mediated systems and pumps. We, therefore, suggest further studies of other extreme environments (or ecosystems) and their associated physicochemical parameters (or factors) in the rise of antibiotic resistance.

Exposure of normal human melanocytes to a tumor promoting phorbol ester reverses growth suppression by transforming growth factor beta.

Transforming growth factor-beta (TGF-beta), a potent inhibitor of normal melanocyte growth, does not significantly suppress growth of melanoma cells. The mechanism of melanocyte desensitization to TGF-beta in the transformation process remains largerly unknown. We investigated whether the tumor promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) may induce melanocyte resistance to TGF-beta. Cell proliferation and DNA synthesis of normal human melanocytes were strongly inhibited by TGF-beta, whereas in the presence of TPA remained largerly unaffected. The inactive phorbol ester 4alpha-phorbol 12,13 didecanoate did not modify the TGF-beta antiproliferative effect, whereas the diacylglycerol analog 1-oleoyl-2-acetyl-sn-glycerol counteracted TGF-beta effects. Protein kinase C (PKC) is the major cellular receptor of tumor promoting phorbol esters. PKC-alpha expression and phosphorylation were almost completely downregulated under combined treatment with TGF-beta + TPA at 24 and 72 h, as shown by immunoblots. Confocal microscopy demonstrated that TGF-beta-induced nuclear accumulation of PKC-alpha was abolished in the presence of TPA at the same time points. The selective PKC inhibitor Ro-31-8220 weakened the TGF-beta antiproliferative effect. Smads are central mediators for TGF-beta signal transduction. Smad-dependent transcriptional activity was suppressed in TGF-beta-treated melanocytes in the presence of TPA, as well as in ALK5 (constitutively active type I TGF-beta receptor)- or Smad3 + Smad4-transfected melanocytes in the presence of Ro-31-8220. In addition, an antisense oligodeoxynucleotide against PKC-alpha abolished TGF-beta-driven Smad-mediated transcription. These findings show that tumor promoting phorbol esters induce melanocyte resistance to TGF-beta, associated with downregulation of PKC-alpha and suppression of Smad-dependent transcription. This may represent an important mechanism for expansion of melanocytes exposed to PKC-targeting tumor promoters.