Affiliation:
1. Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
2. Department of Chemistry, Eastern Michigan University, Ypsilanti, Michigan, USA
Abstract
ABSTRACT
Gram-negative bacteria express a number of sophisticated secretion systems to transport virulence factors across the cell envelope, including the type II secretion (T2S) system. Genes for the T2S components GspC through GspN and PilD are conserved among isolates of
Acinetobacter baumannii
, an increasingly common nosocomial pathogen that is developing multidrug resistance at an alarming rate. In contrast to most species, however, the T2S genes are dispersed throughout the genome rather than linked into one or two operons. Despite this unique genetic organization, we show here that the
A. baumannii
T2S system is functional. Deletion of
gspD
or
gspE
in
A. baumannii
ATCC 17978 results in loss of secretion of LipA, a lipase that breaks down long-chain fatty acids. Due to a lack of extracellular lipase, the
gspD
mutant, the
gspE
mutant, and a
lipA
deletion strain are incapable of growth on long-chain fatty acids as a sole source of carbon, while their growth characteristics are indistinguishable from those of the wild-type strain in nutrient-rich broth. Genetic inactivation of the T2S system and its substrate, LipA, also has a negative impact on
in vivo
fitness in a neutropenic murine model for bacteremia. Both the
gspD
and
lipA
mutants are outcompeted by the wild-type strain as judged by their reduced numbers in spleen and liver following intravenous coinoculation. Collectively, our findings suggest that the T2S system plays a hitherto-unrecognized role in
in vivo
survival of
A. baumannii
by transporting a lipase that may contribute to fatty acid metabolism.
IMPORTANCE
Infections by multidrug-resistant
Acinetobacter baumannii
are a growing health concern worldwide, underscoring the need for a better understanding of the molecular mechanisms by which this pathogen causes disease. In this study, we demonstrated that
A. baumannii
expresses a functional type II secretion (T2S) system that is responsible for secretion of LipA, an extracellular lipase required for utilization of exogenously added lipids. The T2S system and the secreted lipase support
in vivo
colonization and thus contribute to the pathogenic potential of
A. baumannii
.
Funder
HHS | NIH | National Institute of Allergy and Infectious Diseases
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
54 articles.
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