Characterization of two resuscitation promoting factors of Listeria monocytogenes (original) (raw)
Related papers
BMC genomics, 2005
In Micrococcus luteus growth and resuscitation from starvation-induced dormancy is controlled by the production of a secreted growth factor. This autocrine resuscitation-promoting factor (Rpf) is the founder member of a family of proteins found throughout and confined to the actinobacteria (high G + C Gram-positive bacteria). The aim of this work was to search for and characterise a cognate gene family in the firmicutes (low G + C Gram-positive bacteria) and obtain information about how they may control bacterial growth and resuscitation. In silico analysis of the accessory domains of the Rpf proteins permitted their classification into several subfamilies. The RpfB subfamily is related to a group of firmicute proteins of unknown function, represented by YabE of Bacillus subtilis. The actinobacterial RpfB and firmicute YabE proteins have very similar domain structures and genomic contexts, except that in YabE, the actinobacterial Rpf domain is replaced by another domain, which we ha...
Molecular determinants of Listeria monocytogenes pathogenesis
Infection and immunity, 1992
Listeria monocytogenes is a rapidly growing, gram-positive, food-borne human and animal pathogen responsible for serious infections in immunocompromised individuals and pregnant women (17). The murine model of listeriosis has received enormous attention over the years because of the utility of L. monocytogenes as a model pathogen to study cell-mediated immunity. In fact, much of our current understanding of cell-mediated immunity, such as the concept of the activated macrophage, has its roots in the study of murine listeriosis . The beauty of the murine model is that it provides a highly reproducible system for the quantitation of L. monocytogenes virulence. However, until relatively recently almost nothing was known about the cell biology of intracellular growth or bacterial determinants of pathogenicity.
Evidence for involvement of ActA in maturation of the Listeria monocytogenes phagosome
2016
Listeria monocytogenes (Lm) a gram-positive facultative bacterium, is the causative agent of listeriosis, a food-borne disease affecting humans [1]. During infections, Lm is enters phagosomes from which it escapes into the cytoplasm. Listeriolysin O (LLO) is essential and two phospholipases play a role in this process [1]. Actin polymerization provides the propulsive force that moves bacteria through the cytoplasm and into adjacent cells. It is initiated by the interaction of the N-terminal domain of ActA, a 639 amino acid membrane protein, with the host Arp2/3 complex. The first 156 amino acids of the NH2-terminal domain contain three regions that contribute to actin nucleation: a stretch of acidic residues (‘A ’ region, amino acids 32–45), a cofilin homology sequence (‘C ’ region, amino acids 145–156), and an actin monomer-binding region (‘AB ’ region, amino acids 59–102) [2]. Many studies have dissected the function of ActA in actin polymerization. In the present study, we have e...
virulence, 2011
Listeria monocytogenes is an intracellular Gram-positive pathogen and the etiological agent of listeriosis, a human foodborne disease potentially fatal for certain risk groups. The virulence of L. monocytogenes is supported by a highly complex and coordinated intracellular life cycle that comprises several crucial steps: host cell adhesion and invasion, intracellular multiplication and motility, and intercellular spread. The completion of each stage is dependent on the orchestrated activity of specialized bacterial factors, in turn tightly controlled by a specific set of regulators. Some virulence factors and modulators also assume an important role in bacterial resistance and evasion to host defense mechanisms. In the last years, the advent of genomics promoted an increasingly prolific identification and functional characterization of new Listeria virulence factors. In this review, we summarize the current knowledge on nearly 50 molecules deployed by L. monocytogenes to promote its cell infection cycle.
Journal of cell science, 2000
The recruitment of actin to the surface of intracellular Listeria monocytogenes and subsequent tail formation is dependent on the expression of the bacterial surface protein ActA. Of the different functional domains of ActA identified thus far, the N-terminal region is absolutely required for actin filament recruitment and intracellular motility. Mutational analysis of this domain which abolished actin recruitment by intracellular Listeria monocytogenes identified two arginine residues within the 146-KKRRK-150 motif that are essential for its activity. More specifically, recruitment of the Arp2/3 complex to the bacterial surface, as assessed by immunofluorescence staining with antibodies raised against the p21-Arc protein, was not obtained in these mutants. Consistently, treatment of infected cells with latrunculin B, which abrogated actin filament formation, did not affect association of ActA with p21-Arc at the bacterial surface. Thus, the initial recruitment of the Arp2/3 complex...
Molecular Microbiology, 2003
The facultative intracellular bacterial pathogen Listeria monocytogenes dramatically increases the expression of several key virulence factors upon entry into the host cell cytosol. actA , the protein product of which is required for cell-to-cell spread of the bacterium, is expressed at low to undetectable levels in vitro and increases in expression more than 200fold after L. monocytogenes escape from the phagosome. To identify bacterial factors that participate in the intracellular induction of actA expression, L. monocytogenes mutants expressing high levels of actA during in vitro growth were selected after chemical mutagenesis. The resulting mutant isolates displayed a wide range of actA expression levels, and many were less sensitive to environmental signals that normally mediate repression of virulence gene expression. Several isolates contained mutations affecting actA gene expression that mapped at least 40 kb outside the PrfA regulon, supporting the existence of additional regulatory factors that contribute to virulence gene expression. Two actA in vitro expression mutants contained novel mutations within PrfA, a key regulator of L. monocytogenes virulence gene expression. PrfA E77K and PrfA G155S mutations resulted in high-level expression of PrfAdependent genes, increased bacterial invasion of epithelial cells and increased virulence in mice. Both prfA mutant strains were significantly less motile than wild-type L. monocytogenes. These results suggest that, although constitutive activation of PrfA and PrfA-dependent gene expression may enhance L. monocytogenes virulence, it may conversely hamper the bacterium's ability to compete in environments outside host cells. 1538 L. M. Shetron-Rama et al.
Journal of medical microbiology, 2015
Listeria monocytogenes encodes a transcriptional activator PrfA to positively regulate the expression of virulence factors. We describe a strain M7 containing a PrfA*(G145S) that activates expression of virulence factors but with low pathogenicity. To uncover this contradictory relationship, we exchanged the prfA genes between strains EGDe and M7 (designated as EGDe-prfAM7 and M7-prfAEGDe). Constitutive activation of PrfA potentiated virulence of the pathogenic strain EGDe shown as increased adhesive and invasive abilities as well as enhanced cell-cell spread in cultured cell lines. However, the strain M7, though PrfA-activated, had significant defects in these virulence-related phenotypes and low pathogenicity in the murine infection model, as compared with EGDe or EGDe-PrfAM7 (PrfA*). To further uncover the possible mechanisms, we analyzed abundance and distributions of InlA, InlB, LLO and ActA proteins, all regulated by PrfA, in EGDe, M7 and their prfA mutants. Western blotting s...
Negative control of Listeria monocytogenes virulence genes by a diffusible autorepressor
Molecular Microbiology, 2004
Virulence genes from the facultative intracellular pathogen Listeria mono cytogenes are controlled by the transcriptional regulator PrfA. Although PrfA synthesis is activated at 37 ∞ ∞ ∞ ∞ C, PrfA-dependent expression remains low in rich medium. However, a strong induction of the PrfA regulon is observed when L. monocytogenes is cultured in the presence of activated charcoal. Here, we show that the 'charcoal effect' results from the adsorption of a diffusible autorepressor substance released by L. monocytogenes during exponential growth. Analyses using an L. monocytogenes strain in which the prfA gene is expressed constitutively at 37 ∞ ∞ ∞ ∞ C from a plasmid indicate that the autoregulatory substance represses PrfA-dependent expression by inhibiting PrfA activity. PrfA presumably functions via an allosteric activation mechanism. The inhibitory effect is bypassed by a PrfA* mutation that locks PrfA in fully active conformation, suggesting that the autorepressor interferes with the allosteric shift of PrfA. Our data indicate that the listerial autorepressor is a low-molecular-weight hydrophobic substance. We suggest that this diffusible substance mediates a quorum-sensing mechanism by which L. monocytogenes restricts the expression of its PrfA virulence regulon. This autoregulatory pathway could serve L. monocytogenes to ensure the silencing of virulence genes during extracellular growth at 37 ∞ ∞ ∞ ∞ C. It may also play a role during intracellular infection, by limiting the damage to the host cell caused by an excess production of cytotoxic PrfA-dependent virulence factors in the PrfA-activating cytosolic compartment.