Project description:Analysis of the effect of human pleural fluid on the transcriptome of Acinetobacter baumanii A118 Acinetobacter baumannii (Ab) is one of the most treacherous pathogens among those causing hospital-acquired pneumonia (HAP). A. baumannii possesses an adaptable physiology, seen not only in its antibiotic resistance and virulence phenotypes, but also in its metabolic versatility. In this study, we observed that A. baumannii undergoes global transcriptional changes in response to human pleural fluid (PF), a key host-derived environmental signal. Differential gene expression analyses combined with experimental approaches revealed changes in A. baumannii metabolism, affecting cytotoxicity, persistence, bacterial killing and chemotaxis. Over 55% of the differentially expressed transcriptomic genes corresponded to metabolic processes, including the up regulation of glutamate, short chain fatty acid, and styrene metabolism. We observed an up regulation of the pyruvate dehydrogenase complex and found that pyruvate (PYR), in conjunction with PF, triggers an A. baumannii pathogenic behavior that adversely impacts human epithelial cell viability. Interestingly, PF also amplified A. baumannii cytotoxicity against murine macrophages, suggesting an immune evasion strategy implemented by A. baumannii. Moreover, we uncovered opposing metabolic strategies dependent on the degree of pathogenicity of the strains, where less pathogenic strains demonstrated greater utilization of PYR to promote persister formation in the presence of PF. Additionally, our transcriptomic analysis and growth studies of A. baumannii suggest the existence of an alternative phenylalanine (PA) catabolic route independent of the phenylacetic acid pathway, which converts PA to phenylpyruvate (PP) and shuttles intermediates into styrene metabolism. This alternative route promoted a neutrophil-evasive state, as PF-induced degradation of PP significantly reduced overall human neutrophil chemotaxis in ex vivo chemotactic assays. Taken together, these data highlights A. baumannii pathoadaptabililty in response to host signals and provide further insight into the role of bacterial metabolism in virulence traits, antibiotic persistence strategies, and host innate immune evasion.
Project description:Acinetobacter baumannii A1S_1874 gene encodes as a LysR-type transcriptional regulator. LysR family regulators known to regulate biofilm formation, antibiotic resistance, and the expression of diverse genes in other Gram-negative bacteria. However, A1S-1874 has never been characterized in Acinetobacter baumannii, and the studies about the regulon of A1S-1874 are not discovered. In this study we revealed that A1S_1874 differentially regulates at least 302 genes including the csu pilus operon, N-acylhomoserine lactone synthese gene, A1S_0112-A1S_0118 operon, type 1v secretion system related genes that are involved in biofilm formation, surface motility, adherence, quorum sensing and virulence. Overall, our data suggests that A1S-1874 is a key regulator of Acinetobacter baumannii biofilm formation and gene expression.
Project description:In the present work we compare the gene expression profile of A. baumannii and a mutant knock-out strain of A. baumannii lacking a small RNA gene 13573 and the corresponding small RNA 13573 over-producing strain. The main objective is to recognize the main pathways in which the small RNA 13573 is involved. Moreover, the same wild type strain was used to infect mice and was further analyzed after the infection with the aim of finding genes differentially expressed in vivo. Three biological replicates have been performed for each comparison. The RNA collection from Acinetobacter baumannii strain over-expresing the small RNA (sample 13573) was compared with this isolated from A. baumannii harboring the empty vector (PETRA sample) while gene expression in the knock-out strain (KO sample) was compared with the wild type strain Acinetobacter baumannii ATCC 17978 (ATCC sample). The RNA from A.baumannii recovered from the infected animals (INF sample) was compared with the wild type (ATCC).
Project description:Acinetobacter baumannii possesses a single divergent luxR/luxI-type quorum sensing (QS) locus named abaR/abaI. This locus also contains a third gene located between abaR and abaI which we term abaM that codes for an uncharacterized member of the RsaM protein family known to regulate N-acylhomoserine lactone (AHL) dependent QS and the expression of diverse genes in other β- and γ-proteobacteria. However, abaM has never been charatcerized in Acinetobacter baumannii, and the studies about the regulon of abaI are limited. In this study we revealed that AbaM differentially regulates at least 76 genes including the csu pilus operon and the acinetin 505 lipopeptide biosynthetic operon, that are involved in surface adherence, biofilm formation and virulence. A comparison of the wild type, abaM::Tn26 and abaI::Tn26 transcriptomes, indicates that AbaM regulates ~21% of the QS regulon including the csu operon. Moreover, the QS genes (abaI/abaR) were among the most upregulated in the abaM::Tn26 mutant. Overall, our data suggests that abaM is a key regulator of Acinetobacter baumannii QS and gene expression.
