Evolution of Subfamily I.1 Lipases in Pseudomonas aeruginosa

Molecular cloning and heterologous expression of lipase gene from Pseudomonas aeruginosa in Escherichia coli

Lipases, enzymes that perform the hydrolysis of triglycerides into fatty acids and glycerol, present a potential paradigm shift in the realms of food and detergent industries. Their enhanced efficiency, energy conservation and environmentally friendly attributes make them promising substitutes for chemical catalysts. Motivated by this prospect, this present study was targeted on the heterologous expression of a lipase gene, employing E. coli as the host organism. The lipase gene was sourced from Pseudomonas aeruginosa genomic DNA open reading frame spanning 936 bp by PCR using gene-specific primers. Initial cloning into the T/A vector (pTZ57 R/T) and subsequent sub-cloning into the pET-28a(+) bacterial expression vector. Transformation into E. coli BL21 codon plus strain ensued for the expression of the recombinant protein which was induced at 37 °C. The recombinant lipase protein was purified by immobilized metal ion chromatography. The Optimal activity of the recombinant enzyme was found to be at 40 °C and pH 8.0. The partial purified lipase exhibited a specific activity of 6595.71 U/mg in the dialyzed fraction, markedly surpassing the crude fraction's 1182.87 U/mg.

Evolution and function analysis of glycerol kinase GlpK in Pseudomonasaeruginosa

Pseudomonas aeruginosa is a Gram-negative bacterium capable of widespread niches, which is also one of the main bacteria that cause patient infection. The metabolic diversity of Pseudomonas aeruginosa is an essential factor in adapting to a variety of environments. Based on the previous studies, adaptive genetic variation in the glycerol kinase GlpK, the glycerol 3-phosphotransferase, contributes to the fitness of bacteria in human bodies, such as Mycobacterium tuberculosis and Escherichia coli. Thus, this study aimed to explore the molecular evolution and function of glpK in P. aeruginosa. Using extensive population genomic data, we have identified the prevalence of two glpK copies in P. aeruginosa that clustered into distinct branches, which were later known as Clade 1 and 2. The evolution analysis revealed that glpK in Clade 1 derived from an ancestral P. aeruginosa species and the other from an ancient horizontal gene transfer event. In addition, we confirmed that the GlpK in Clade 2 still retained glycerol kinase activity but was much weaker than that of GlpK in Clade 1. We demonstrated the importance of the critical amino acid Q70 in GlpK glycerol kinase activity by point mutation. Furthermore, Co-expression network analysis implied that the two glpK copies of P. aeruginosa regulate separate networks and may be a strategy to improve fitness in P. aeruginosa.

Y12F mutation in Pseudomonas plecoglossicida S7 lipase enhances its thermal and pH stability for industrial applications: a combination of in silico and in vitro study

Appropriate amino acid substitutions are critical for protein engineering to redesign catalytic properties of industrially important enzymes like lipases. The present study aimed for improving the environmental stability of lipase from Pseudomonas plecoglossicida S7 through site-directed mutagenesis driven by computational studies. lipA gene was amplified and sequenced. Both wild type (WT) and mutant type (MT) lipase genes were expressed into the pET SUMO system. The expressed proteins were purified and characterized for pH and thermostability. The lipase gene belonged to subfamily I.1 lipase. Molecular dynamics revealed that Y12F-palmitic acid complex had a greater binding affinity (-6.3 Kcal/mol) than WT (-6.0 Kcal/mol) complex. Interestingly, MDS showed that the binding affinity of WT-complex (-130.314 ± 15.11 KJ/mol) was more than mutant complex (-108.405 ± 69.376 KJ/mol) with a marked increase in the electrostatic energy of mutant (-26.969 ± 12.646 KJ/mol) as compared to WT (-15.082 ± 13.802 KJ/mol). Y12F mutant yielded 1.27 folds increase in lipase activity at 55 °C as compared to the purified WT protein. Also, Y12F mutant showed increased activity (~ 1.2 folds each) at both pH 6 and 10. P. plecoglossicida S7. Y12F mutation altered the kinetic parameters of MT (K_m- 1.38 mM, V_max- 22.32 µM/min) as compared to WT (K_m- 1.52 mM, V_max- 29.76 µM/min) thus increasing the binding affinity of mutant lipase. Y12F mutant lipase with better pH and thermal stability can be used in biocatalysis.

Phylogenomic and comparative genomic studies robustly demarcate two distinct clades of Pseudomonas aeruginosa strains: proposal to transfer the strains from an outlier clade to a novel species Pseudomonas paraeruginosa sp. nov

The strains of Pseudomonas aeruginosa exhibit considerable differences in their genotypic and pathogenic properties. To clarify their evolutionary/taxonomic relationships, comprehensive phylogenomic and comparative genomic studies were conducted on the genome sequences of 212 P . aeruginosa strains covering their genetic diversity. In a phylogenomic tree based on 118 conserved proteins, the analysed strains formed two distinct clades. One of these clades, Clade-1, encompassing >70 % of the strains including the type strain DSM 50071T, represents the species P. aeruginosa sensu stricto. Clade-2, referred to in earlier work as the outlier group, with NCTC 13628T as its type strain, constitutes a novel species level lineage. The average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between the strains from Clade-1 and Clade-2 are in the range of 93.4–93.7, 95.1–95.3 and 52–53 %, respectively. The 16S rRNA gene of P. aeruginosa DSM 50071T also shows 98.3 % similarity to that of NCTC 13628T. These values are lower than the suggested cut-off values for species distinction, indicating that the Clade-2 strains (NCTC 13628T) constitute a new species. We also report the identification of 12 conserved signature indels in different proteins and 24 conserved signature proteins that are exclusively found in either Clade-1 or Clade-2, providing a reliable means for distinguishing these clades. Additionally, in contrast to swimming motility, twitching motility is only present in Clade-1 strains. Based on earlier work, the strains from these two clades also differ in their pathogenic mechanisms (presence/absence of Type III secretion system), production of biosurfactants, phenazines and siderophores, and several other genomic characteristics. Based on the evidence from different studies, we propose that the Clade-2 strains constitute a novel species for which the name Pseudomonas paraeruginosa is proposed. The type strain is NCTC 13628T (=PA7T=ATCC 9027T). The description of Pseudomonas aeruginosa is also emended to include information for different molecular markers specific for this species.

Virulence Factors of Pseudomonas Aeruginosa and Antivirulence Strategies to Combat Its Drug Resistance

Pseudomonas aeruginosa is an opportunistic pathogen causing nosocomial infections in severely ill and immunocompromised patients. Ubiquitously disseminated in the environment, especially in hospitals, it has become a major threat to human health due to the constant emergence of drug-resistant strains. Multiple resistance mechanisms are exploited by P. aeruginosa, which usually result in chronic infections difficult to eradicate. Diverse virulence factors responsible for bacterial adhesion and colonization, host immune suppression, and immune escape, play important roles in the pathogenic process of P. aeruginosa. As such, antivirulence treatment that aims at reducing virulence while sparing the bacterium for its eventual elimination by the immune system, or combination therapies, has significant advantages over traditional antibiotic therapy, as the former imposes minimal selective pressure on P. aeruginosa, thus less likely to induce drug resistance. In this review, we will discuss the virulence factors of P. aeruginosa, their pathogenic roles, and recent advances in antivirulence drug discovery for the treatment of P. aeruginosa infections.