ABSTRACT
Acinetobacter baumannii is an emerging bacterial pathogen of considerable medical concern. The organism's transmission and ability to cause disease has been associated with its propensity to colonize and form biofilms on abiotic surfaces in health care settings. To better understand the genetic determinants that affect biomaterial attachment, we performed a transposon mutagenesis analysis of abiotic surface-colonization using A. baumannii strain 98-37-09. Disruption of an RNase T2 family gene was found to limit the organism's ability to colonize polystyrene, polypropylene, glass, and stainless steel surfaces. DNA microarray analyses revealed that in comparison to wild type and complemented cells, the RNase T2 family mutant exhibited reduced expression of 29 genes, 15 of which are predicted to be associated with bacterial attachment and surface-associated motility. Motility assays confirmed that RNase T2 mutant displays a severe motility defect. Taken together, our results indicate that the RNase T2 family protein identified in this study is a positive regulator of A. baumannii's ability to colonize inanimate surfaces and motility. Moreover, the enzyme may be an effective target for the intervention of biomaterial colonization, and consequently limit the organism's transmission within the hospital setting.
Subject(s)
Acinetobacter baumannii/enzymology , Acinetobacter baumannii/physiology , Endoribonucleases/metabolism , Acinetobacter baumannii/genetics , Bacterial Adhesion/genetics , Bacterial Adhesion/physiology , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Biocompatible Materials , Endoribonucleases/genetics , Oligonucleotide Array Sequence Analysis , Polystyrenes/chemistryABSTRACT
Acinetobacter baumannii has emerged as a bacterial pathogen of considerable healthcare concern. Yet, little is known about the organism's basic biological processes and the regulatory networks that modulate expression of its virulence factors and antibiotic resistance. Using Affymetrix GeneChips , we comprehensively defined and compared the transcriptomes of two A. baumannii strains, ATCC 17978 and 98-37-09, during exponential and stationary phase growth in Luria-Bertani (LB) medium. Results revealed that in addition to expected growth phase-associated metabolic changes, several putative virulence factors were dramatically regulated in a growth phase-dependent manner. Because a common feature between the two most severe types of A. baumannii infection, pneumonia and septicemia, includes the organism's dissemination to visceral organs via the circulatory system, microarray studies were expanded to define the expression properties of A. baumannii during growth in human serum. Growth in serum significantly upregulated iron acquisition systems, genes associated with epithelial cell adherence and DNA uptake, as well as numerous putative drug efflux pumps. Antibiotic susceptibility testing verified that the organism exhibits increased antibiotic tolerance when cultured in human serum, as compared to LB medium. Collectively, these studies provide researchers with a comprehensive database of A. baumannii's expression properties in LB medium and serum and identify biological processes that may contribute to the organism's virulence and antibiotic resistance.
