Involvement of the Histone-Like Nucleoid Structuring Protein (H-NS) in Acinetobacter baumannii’s Natural Transformation

LE, CASIN; PIMENTEL, CAMILA (CO-FIRST AUTHOR); TUTTOBENE, MARISEL R.; SUBILS, TOMÁS; ESCALANTE, JENNY; NISHIMURA, BRENT; ARRIAGA, SUSANA; RODGERS, DEJA; BONOMO, ROBERT A.; SIEIRA, RODRIGO; TOLMASKY, MARCELO E.; RAMÍREZ, MARÍA SOLEDAD

Pathogens

MDPI

Año: 2021 vol. 10

Most Acinetobacter baumannii strains are naturally competent. Although some informationis available about factors that enhance or reduce the frequency of the transformation of this bacterium,the regulatory elements and mechanisms are barely understood. In this article, we describe studieson the role of the histone-like nucleoid structuring protein, H-NS, in the regulation of the expressionof genes related to natural competency and the ability to uptake foreign DNA. The expressionlevels of the natural transformation-related genes pilA, pilT, pilQ, comEA, comEC, comF, and drpAsignificantly increased in a Dhns derivative of A. baumannii A118. The complementation of the mutantwith a recombinant plasmid harboring hns restored the expression levels of six of these genes (pilTremained expressed at high levels) to those of the wild-type strain. The transformation frequency ofthe A. baumannii A118 Dhns strain was significantly higher than that of the wild-type. Similar, albeitnot identical, there were consequences when hns was deleted from the hypervirulent A. baumanniiAB5075 strain. In the AB5075 complemented strain, the reduction in gene expression in a few caseswas not so pronounced that it reached wild-type levels, and the expression of comEA was enhancedfurther. In conclusion, the expression of all seven transformation-related genes was enhanced afterdeleting hns in A. baumannii A118 and AB5075, and these modifications were accompanied by anincrease in the cells? transformability. The results highlight a role of H-NS in A. baumannii?s naturalcompetence.