Genome-Wide Analysis Reveals Loci Encoding Anti-Macrophage Factors in the Human Pathogen Burkholderia pseudomallei K96243

Abstract

Burkholderia pseudomallei is an important human pathogen whose infection biology is still poorly understood. The bacterium is endemic to tropical regions, including South East Asia and Northern Australia, where it causes melioidosis, a serious disease associated with both high mortality and antibiotic resistance. B. pseudomallei is a Gram-negative facultative intracellular pathogen that is able to replicate in macrophages. However despite the critical nature of its interaction with macrophages, few anti-macrophage factors have been characterized to date. Here we perform a genome-wide gain of function screen of B. pseudomallei strain K96243 to identify loci encoding factors with anti-macrophage activity. We identify a total of 113 such loci scattered across both chromosomes, with positive gene clusters encoding transporters and secretion systems, enzymes/toxins, secondary metabolite, biofilm, adhesion and signal response related factors. Further phenotypic analysis of four of these regions shows that the encoded factors cause striking cellular phenotypes relevant to infection biology, including apoptosis, formation of actin ‘tails’ and multi-nucleation within treated macrophages. The detailed analysis of the remaining host of loci will facilitate genetic dissection of the interaction of this important pathogen with host macrophages and thus further elucidate this critical part of its infection cycle.

Members of the Salivary Gland Surface Protein (SGS) Family Are Major Immunogenic Components of Mosquito Saliva

“…3B and 6) as well as transcriptomic analyses by others (16,38), SGSs are the only anopheline or culicine saliva proteins whose mass approximates the value predicted for this ϳ387-kDa protein. In support of our hypothesis that Sgs4 and Sgs5 are immunomodulatory, it has recently been shown that bacterial RHS/YD-repeat proteins (distant relatives of SGS) play a role during the deactivation of human macrophages by the bacterial pathogen Burkholderia pseudomallei (39). If SGSs are indeed immunomodulators, they should be considered when developing transmission-blocking vaccines.…”

Transcriptional profiles of Burkholderia pseudomallei reveal the direct and indirect roles of Sigma E under oxidative stress conditions

“…The expression of B. pseudomallei katG and ahpC is regulated through a global H 2 O 2 sensor and the OxyR transcriptional regulator [21–23]. The increased expression of katG and ahpC after exposure to oxidative stress is consistent with the findings from previous studies [22, 23].…”

Melioidosis: molecular aspects of pathogenesis

“…A marked increase in actin stress fiber formation, very similar in effect to BopE, was observed when BPSL1057F1 was expressed in HeLa cells [31]. A mutant of the hypothetical protein BPSL1528 had severely reduced actin tail formation in HeLa cells while expression of the hemagglutanin FhaB (BPSS1727) in J774.2 macrophages yielded actin projections stretching towards adjacent cells [65,87]. The BPSL1528 mutant also displayed reduced swimming motility and intracellular growth in phagocytic and non-phagocytic cells, suggesting BPSL1528 may act pleiotropically in a regulatory manner [65].…”

“…It is possible that RpoS may play a role in regulating the transcription of genes whose products are involved in promoting macrophage fusion [84,92]. Ecotopic expression of BPSL0590 and BPSL0591, putative homologs of Photorhabdus luminescens insecticidal toxins, in J774.2 macrophages induced MNGC formation and nuclear apoptosis [87]. BPSS0945, a putative exported peptidase, localized to the nucleus when expressed in HeLa cells and resulted in increased MNGC formation.…”