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non-culturable legionella pneumophila associated with acanthamoeba castellanii: detection of the bacterium using dna amplification and hybridization.the intracellular localization of legionella pneumophila serogroup 1 within acanthamoeba castellanii rendered the bacteria non-culturable on supplemented bcye agar. dna amplification, using two 19-mer primers, and hybridization using a 25-mer oligonucleotide probe, permitted detection of leg. pneumophila in approximately 81% (29/36) of samples where the bacteria could not be detected using culture. a combination of co-cultivation of samples with leg. pneumophila-naive a. polyphaga or hartmannell ...19957883646
growth of legionella pneumophila in acanthamoeba castellanii enhances invasion.legionella pneumophila is considered to be a facultative intracellular parasite. therefore, the ability of these bacteria to enter, i.e., invade, eukaryotic cells is expected to be a key pathogenic determinant. we compared the invasive ability of bacteria grown under standard laboratory conditions with that of bacteria grown in acanthamoeba castellanii, one of the protozoan species that serves as a natural host for l. pneumophila in the environment. amoeba-grown l. pneumophila cells were found t ...19948039895
resuscitation of viable but nonculturable legionella pneumophila philadelphia jr32 by acanthamoeba castellanii.legionella pneumophila is an aquatic bacterium and is responsible for legionnaires' disease in humans. free-living amoebae are parasitized by legionellae and provide the intracellular environment required for the replication of this bacterium. in low-nutrient environments, however, l. pneumophila is able to enter a non-replicative viable but nonculturable (vbnc) state. in this study, l. pneumophila philadelphia i jr 32 was suspended in sterilized tap water at 10(4) cells/ml. the decreasing numbe ...19979143134
the legionella pneumophila rpos gene is required for growth within acanthamoeba castellanii.to investigate regulatory networks in legionella pneumophila, the gene encoding the homolog of the escherichia coli stress and stationary-phase sigma factor rpos was identified by complementation of an e. coli rpos mutation. an open reading frame that is approximately 60% identical to the e. coli rpos gene was identified. western blot analysis showed that the level of l. pneumophila rpos increased in stationary phase. an insertion mutation was constructed in the rpos gene on the chromosome of l. ...199910438758
influence of acanthamoeba castellanii on intracellular growth of different legionella species in human monocytes.previous studies using a murine model of coinhalation of legionella pneumophila and hartmannella vermiformis have shown a significantly enhanced intrapulmonary growth of l. pneumophila in comparison to inhalation of legionellae alone (j. brieland, m. mcclain, l. heath, c. chrisp, g. huffnagle, m. legendre, m. hurley, j. fantone, and c. engleberg, infect. immun. 64:2449-2456, 1996). in this study, we introduce an in vitro coculture model of legionellae, mono mac 6 cells (mm6) and acanthamoeba cas ...200010698751
molecular and functional characterization of type i signal peptidase from legionella pneumophila.legionella pneumophila is a facultative intracellular gram-negative rod-shaped bacterium that has become an important cause of both community-acquired and nosocomial pneumonia. numerous studies concerning the unravelling of the virulence mechanism of this important pathogen have been initiated. as evidence is now accumulating for the involvement of protein secretion systems in bacterial virulence in general, the type i signal peptidase (lepb) of l. pneumophila was of particular interest. this en ...200415133109
evidence that hsp90 is involved in the altered interactions of acanthamoeba castellanii variants with bacteria.there are many similarities between the interactions of environmental protozoa with pathogenic bacterial species and those observed in mammalian macrophages. since single-celled protozoa predate mammalian hosts, it is likely that interactions in environmental biofilms have selected for many of the bacterial virulence mechanisms responsible for human disease. in order to better understand bacterial-phagocyte interactions, we developed a selection for acanthamoeba castellanii variants that are mor ...200415189979
reduced expression of the global regulator protein csra in legionella pneumophila affects virulence-associated regulators and growth in acanthamoeba castellanii.legionella bacteria have a developmental cycle in which they go from existing in the aquatic environment to replicating inside eukaryotic host cells. the adaptation to the new environment requires an efficient regulatory system. overexpression of csra, a global regulatory protein found in a variety of gram-negative bacteria has been shown to suppress virulence-associated traits in legionella pneumophila. since evidence resulting only from overproduction may not be sufficient to validate the role ...200415293450
coevolution between nonhomologous but functionally similar proteins and their conserved partners in the legionella pathogenesis system.legionella pneumophila, the causative agent of legionnaires' disease, and other pathogenic legionella species multiply inside protozoa and human macrophages by using the intracellular multiplication (icm)/defect in organelle trafficking (dot) type-iv secretion system. the icmq protein, which possesses pore-forming activity, and icmr, which regulates the icmq activity, are two essential components of this system. analysis of the region expected to contain these two genes from 29 legionella specie ...200516091472
virulence strategies for infecting phagocytes deduced from the in vivo transcriptional program of legionella pneumophila.adaptation to the host environment and exploitation of host cell functions are critical to the success of intracellular pathogens. here, insight to these virulence mechanisms was obtained for the first time from the transcriptional program of the human pathogen legionella pneumophila during infection of its natural host, acanthamoeba castellanii. the biphasic life cycle of l. pneumophila was reflected by a major shift in gene expression from replicative to transmissive phase, concerning nearly h ...200616882028
sel1 repeat protein lpne is a legionella pneumophila virulence determinant that influences vacuolar trafficking.the environmental pathogen legionella pneumophila possesses five proteins with sel1 repeats (slrs) from the tetratricopeptide repeat protein family. three of these proteins, lpne, enhc, and lidl, have been implicated in the ability of l. pneumophila to efficiently establish infection and/or manipulate host cell trafficking events. previously, we showed that lpne is important for l. pneumophila entry into macrophages and epithelial cells. in further virulence studies here, we show that lpne is al ...200717893138
expression of legionella pneumophila paralogous lipid a biosynthesis genes under different growth conditions.legionella pneumophila is an opportunistic pathogen that in the environment colonizes biofilms and replicates within amoebae. the bacteria employ the intracellular multiplication/defective organelle trafficking (icm/dot) type iv secretion system to grow intracellularly in a specific vacuole. using acanthamoeba castellanii as a host cell, we have previously identified lcsc (legionella cytotoxic suppressor), a paralogue of the lipid a disaccharide synthase lpxb, as a cytotoxic factor of l. pneumop ...200717975091
a faster and more accurate assay for intracellular replication of legionella pneumophila in amoebae hosts.a faster, more sensitive, and more accurate method to study intracellular replication of legionella pneumophila in amoeboid hosts is described. this assay relies on an automated plate-reader to examine the intracellular growth and release of bacteria in real-time. our experiments using this method have already revealed new insights into the kinetics of intracellular replication of l. pneumophila in acanthamoeba castellanii.200818077026
proteomic characterization of the whole secretome of legionella pneumophila and functional analysis of outer membrane vesicles.secretion of effector molecules is one of the major mechanisms by which the intracellular human pathogen legionella pneumophila interacts with host cells during infection. specific secretion machineries which are responsible for the subfraction of secreted proteins (soluble supernatant proteins [ssps]) and the production of bacterial outer membrane vesicles (omvs) both contribute to the protein composition of the extracellular milieu of this lung pathogen. here we present comprehensive proteome ...200818250176
lgt: a family of cytotoxic glucosyltransferases produced by legionella pneumophila.legionella pneumophila is a facultative intracellular pathogen responsible for severe lung disease in humans, known as legionellosis or legionnaires' disease. previously, we reported on the approximately 60-kda glucosyltransferase (lgt1) from legionella pneumophila, which modified eukaryotic elongation factor 1a. in the present study, using l. pneumophila philadelphia-1, lens, paris, and corby genome databases, we identified several genes coding for proteins with considerable sequence homology t ...200818281405
synergistic contribution of the legionella pneumophila lqs genes to pathogen-host interactions.the causative agent of legionnaires' disease, legionella pneumophila, is a natural parasite of environmental protozoa and employs a biphasic life style to switch between a replicative and a transmissive (virulent) phase. l. pneumophila harbors the lqs (legionella quorum sensing) cluster, which includes genes encoding the autoinducer synthase lqsa, the sensor kinase lqss, the response regulator lqsr, and a homologue of hded, which is involved in acid resistance in escherichia coli. lqsr promotes ...200818805977
heterogeneity in chlorine susceptibility for legionella pneumophila released from acanthamoeba and hartmannella.to assess chlorine susceptibility of legionella pneumophila grown from two amoebic hosts, acanthamoeba castellanii and hartmannella vermiformis.200919040705
survey of pathogenic free-living amoebae and legionella spp. in mud spring recreation area.acanthamoeba, hartmannella, and naegleria are free-living amoebae, ubiquitous in aquatic environments. several species within these genera are recognized as potential human pathogens. these free-living amoebae may facilitate the proliferation of their parasitical bacteria, such as legionella. in this study, we identified acanthamoeba, hartmannella, naegleria, and legionella using various analytical procedures and investigated their occurrence at a mud spring recreation area in taiwan. we investi ...200919457534
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