Extracellular stress and lipopolysaccharide modulate Acinetobacter baumannii surface-associated motility

McQueary, Christin N.; Kirkup, Benjamin C.; Si, Yuanzheng; Barlow, Miriam; Actis, Luis A.; Craft, David W.; Zurawski, Daniel V.

doi:10.1007/s12275-012-1555-1

Cited by 71 publications

(63 citation statements)

References 81 publications

(85 reference statements)

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“…To determine if stress influenced the frequency of phase variation, cells were tested in LB under stress conditions similar to those reported by McQueary et al (33). These conditions include high salt (300 mM NaCl), no salt, H 2 O 2 (50 M), low iron (100 M 2,2=-dipyridyl), high iron (100 M FeCl 3 ), EDTA (100 M), and ethanol (1%).…”

Section: Resultsmentioning

confidence: 99%

Phase-Variable Control of Multiple Phenotypes in Acinetobacter baumannii Strain AB5075

2015

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Acinetobacter baumannii strain AB5075 produces colonies with two opacity phenotypes, designated opaque and translucent. These phenotypes were unstable and opaque and translucent colony variants were observed to interconvert at high frequency, suggesting that a phase-variable mechanism was responsible. The frequency of phase variation both within colonies and in broth cultures increased in a cell density-dependent manner and was mediated by the accumulation of an extracellular factor. This factor was distinct from the known A. baumannii signaling molecule 3-OH C 12 -homoserine lactone. Opaque and translucent colony variants exhibited a number of phenotypic differences, including cell morphology, surface motility, biofilm formation, antibiotic resistance, and virulence in a Galleria mellonella model. Additional clinical isolates exhibited a similar phase-variable control of colony opacity, suggesting that this may be a common feature of A. baumannii. IMPORTANCEA novel phase-variable mechanism has been identified in Acinetobacter baumannii that results in an interconversion between opaque and translucent colony phenotypes. This phase variation also coordinately regulates motility, cell shape, biofilm formation, antibiotic resistance, and virulence. The frequency of phase variation is increased at high cell density via a diffusible extracellular signal. To our knowledge, this report presents the first example of phase variation in A. baumannii and also the first example of quorum sensing-mediated control of phase variation in a bacterium. The findings are important, as this phase-variable mechanism can be identified only via changes in colony opacity using oblique light; therefore, many researchers studying A. baumannii may unknowingly be working with different colony variants.

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Section: Resultsmentioning

confidence: 99%

Phase-Variable Control of Multiple Phenotypes in Acinetobacter baumannii Strain AB5075

2015

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“…produce LOS but not LPS. In any case, targeted mutagenesis and random mutagenesis of genes involved in synthesis of the LOS core oligosaccharide have shown that this component is a major contributor to Acinetobacter survival and virulence (33)(34)(35). The cluster of genes that synthesize the sugar component of LOS are extremely diverse among Acinetobacter spp., and a number of different structures have been determined or predicted (36).…”

Section: Cell Surfacementioning

confidence: 99%

Pathogenic Acinetobacter: from the Cell Surface to Infinity and Beyond

2016

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The genus Acinetobacter encompasses multiple nosocomial opportunistic pathogens that are of increasing worldwide relevance because of their ability to survive exposure to various antimicrobial and sterilization agents. Among these, Acinetobacter baumannii, Acinetobacter nosocomialis, and Acinetobacter pittii are the most frequently isolated in hospitals around the world. Despite the growing incidence of multidrug-resistant Acinetobacter spp., little is known about the factors that contribute to pathogenesis. New strategies for treating and managing infections caused by multidrug-resistant Acinetobacter strains are urgently needed, and this requires a detailed understanding of the pathobiology of these organisms. In recent years, some virulence factors important for Acinetobacter colonization have started to emerge. In this review, we focus on several recently described virulence factors that act at the bacterial surface level, such as the capsule, O-linked protein glycosylation, and adhesins. Furthermore, we describe the current knowledge regarding the type II and type VI secretion systems present in these strains.

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“…Even though phenotypically distinct, all forms of motility described for A. baumannii have been shown to depend on synthesis of the polyamine 1,3-diaminopropane (26). Surface motility of A. baumannii was further shown to be controlled by blue light sensing (28) and quorum sensing (24,29) and to depend on iron availability (30,31).…”

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confidence: 99%

DNA Uptake by the Nosocomial Pathogen Acinetobacter baumannii Occurs during Movement along Wet Surfaces

Wilharm¹,

Piesker²,

Laue³

et al. 2013

Journal of Bacteriology

109

165

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bThe emergence of Acinetobacter baumannii as an increasingly multidrug-resistant nosocomial pathogen largely relies on acquisition of resistance genes via horizontal gene transfer. Here, we demonstrate that many clinical isolates of A. baumannii take up DNA while they move along wet surfaces. We show that both motility and DNA uptake are abolished after inactivation of pilT, which putatively encodes the type 4 pilus (T4P) retraction ATPase, and comEC, which putatively encodes the DNA uptake channel, respectively. Inactivation of pilT correlates with an increase in the number and length of pili with an average diameter of 7.2 nm. In the Galleria mellonella infection model, the comEC mutant is significantly attenuated, whereas the pilT mutant is not, dissecting biologically distinct roles of T4P and the DNA uptake channel. Collectively, these findings promote our understanding of the mechanisms of DNA uptake and resistance development in A. baumannii, which may also apply to other important pathogens.

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Extracellular stress and lipopolysaccharide modulate Acinetobacter baumannii surface-associated motility

Cited by 71 publications

References 81 publications

Phase-Variable Control of Multiple Phenotypes in Acinetobacter baumannii Strain AB5075

Phase-Variable Control of Multiple Phenotypes in Acinetobacter baumannii Strain AB5075

Pathogenic Acinetobacter: from the Cell Surface to Infinity and Beyond

DNA Uptake by the Nosocomial Pathogen Acinetobacter baumannii Occurs during Movement along Wet Surfaces

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