Klebsiella pneumoniae type VI secretion system-mediated microbial competition is PhoPQ controlled and reactive oxygen species dependent: T6SS luciferase transcriptional data
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ABSTRACT:
ORGANISM(S): Klebsiella pneumoniae
SUBMITTER: Jose Bengoechea
PROVIDER: S-BSST301 | biostudies-other |
REPOSITORIES: biostudies-other
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Project description:Klebsiella pneumoniae is recognized as an urgent threat to human health due to the increasing isolation of multidrug resistant strains. Hypervirulent strains are a major concern due to their ability to cause life-threating infections in healthy hosts. The type VI secretion system (T6SS) is widely implicated in microbial antagonism, and it mediates interactions with host eukaryotic cells in some cases. In silico search for genes orthologous to T6SS component genes and T6SS effector genes across 700 K. pneumoniae genomes shows extensive diversity in T6SS genes across the K. pneumoniae species. Temperature, oxygen tension, pH, osmolarity, iron levels, and NaCl regulate the expression of the T6SS encoded by a hypervirulent K. pneumoniae strain. Polymyxins and human defensin 3 also increase the activity of the T6SS. A screen for regulators governing T6SS uncover the correlation between the transcription of the T6SS and the ability to kill E. coli prey. Whereas H-NS represses the T6SS, PhoPQ, PmrAB, Hfq, Fur, RpoS and RpoN positively regulate the T6SS. K. pneumoniae T6SS mediates intra and inter species bacterial competition. This antagonism is only evident when the prey possesses an active T6SS. The PhoPQ two component system governs the activation of K. pneumoniae T6SS in bacterial competitions. Mechanistically, PhoQ periplasmic domain, and the acid patch within, is essential to activate K. pneumoniae T6SS. Klebsiella T6SS also mediates anti-fungal competition. We have delineated the contribution of each of the individual VgrGs in microbial competition and identified VgrG4 as a T6SS effector. The DUF2345 domain of VgrG4 is sufficient to intoxicate bacteria and yeast. ROS generation mediates the antibacterial effects of VgrG4, and the antitoxin Sel1E protects against the toxic activity of VgrG4. Our findings provide a better understanding of the regulation of the T6SS in bacterial competitions, and place ROS as an early event in microbial competition.
| S-EPMC7108748 | biostudies-literature
Project description:BackgroundKlebsiella pneumoniae (KP) is an opportunistic pathogen that mainly causes respiratory and urinary tract infections. The frequent occurrence of simultaneously virulent and multiple drug-resistant isolates led WHO to include this species in the list of top priorities for research and development of therapeutic alternatives. The comprehensive knowledge of the molecular mechanisms underlying KP virulence may lead to the proposal of more efficient and specific drugs. One of its virulence factors is the Type VI Secretion System (T6SS), which contributes to bacterial competition, cell invasion and in vivo colonisation. Despite the few studies showing the involvement of T6SS in KP pathogenesis, little is known concerning the regulation of its expression. The understanding of regulatory mechanisms may give more clues about the function of the system and the possibilities of future interference in this process. This work aimed to standardise the annotation of T6SS genes in KP strains and identify mechanisms of their transcriptional regulation through computational predictions.ResultsWe analyzed the genomes of Kp52.145, HS11286 and NTUH-K2044 strains to perform a broad prediction and re-annotation of T6SS genes through similarity searches, comparative and linear discriminant analysis. 38 genes were found in Kp52.145, while 29 in HS11286 and 30 in NTUH-K2044. Genes coding for iron uptake systems are encoded in adjacencies of T6SS, suggesting that KP T6SS might also play a role in ion import. Some of the T6SS genes are comprised in syntenic regions. 17 sigma 70-dependent promoter regions were identified in Kp52.145, 12 in HS11286 and 12 in NTUH-K2044. Using VirtualFootprint algorithm, binding sites for 13 transcriptional regulators were found in Kp52.145 and 9 in HS11286 and 17 in NTUH-K2044. Six of them are common to the 3 strains: OxyR, H-NS, RcsAB, GcvA, Fis, and OmpR.ConclusionsThe data presented herein are derived from computational analysis. Although future experimental studies are required to confirm those predictions, they suggest that KP T6SS might be regulated in response to environmental signals that are indeed sensed by the bacteria inside the human host: temperature (H-NS), nutrition-limitation (GcvA and Fis), oxidative stress (OxyR) and osmolarity (RscAB and OmpR).
| S-EPMC6580597 | biostudies-literature
Project description:BackgroundWe previously isolated a Klebsiella pneumoniae strain, NTUH-K2044, from a community-acquired pyogenic liver abscess (PLA) patient. Analysis of the NTUH-K2044 genome revealed that this strain harbors 2 putative type VI secretion system (T6SS)-encoding gene clusters.MethodsThe distribution of T6SS genes in the PLA and intestinal-colonizing K pneumoniae clinical isolates was examined. icmF1-, icmF2-, icmF1/icmF2-, and hcp-deficient K pneumoniae strains were constructed using an unmarked deletion method. The roles of T6SSs in antibacterial activity, type-1 fimbriae expression, cell adhesion, and invasion and intestinal colonization were determined.ResultsThe prevalence of T6SSs is higher in the PLA strains than in the intestinal-colonizing strains (37 of 42 vs 54 of 130). Deletion of icmF1/icmF2 and hcp genes significantly reduced interbacterial and intrabacterial killing. Strain deleted for icmF1 and icmF2 exhibited decreased transcriptional expression of type-1 fimbriae and reduced adherence to and invasion of human colorectal epithelial cells and was attenuated for in vivo competition to enable colonization of the host gut. Finally, Hcp expression in K pneumoniae was silenced by the histone-like nucleoid structuring protein via direct binding.ConclusionsThese results provide new insights into T6SS-mediated bacterial competition and attachment in K pneumoniae and could facilitate the prevention of K pneumoniae infection.
| S-EPMC6350951 | biostudies-literature
Project description:Klebsiella pneumoniae is a nosocomial opportunistic pathogen that can cause pneumonia, liver abscesses, and infections of the bloodstream. The resistance and pathogenicity of K. pneumoniae pose major challenges to clinical practice. However, the ecology and pathogenic mechanisms of K. pneumoniae have not been fully elucidated. Among these mechanisms, the secretion systems encoded by strains of the bacteria confer adaptive advantages depending on the niche occupied. The type VI secretion system (T6SS) is a multi-protein complex that delivers effector proteins to the extracellular environment or directly to eukaryotic or prokaryotic cells. T6SSs are widely distributed in Gram-negative bacteria and play an important role in bacterial virulence and the interactions between bacteria and other microorganisms or the environment. This study aimed to enhance the understanding of the characteristics of T6SSs in K. pneumoniae through an in-depth comparative genomic analysis of the T6SS in 241 sequenced strains of K. pneumoniae. We identified the T6SS loci, the synteny of the loci in different species, as well as the effectors and core T6SS-related genes in K. pneumoniae. The presence of a T6SS was a common occurrence in K. pneumoniae, and two T6SS clusters are the most prevalent. The variable region downstream of the gene vgrG usually encodes effector proteins. Conserved domain analysis indicated that the identified putative effectors in K. pneumoniae had the functions of lipase, ribonuclease, deoxyribonuclease, and polysaccharide hydrolase. However, some effectors did not contain predicted functional domains, and their specific functions have yet to be elucidated. This in silico study represents a detailed analysis of T6SS-associated genes in K. pneumoniae and provides a foundation for future studies on the mechanism(s) of T6SSs, especially effectors, which may generate new insights into pathogenicity and lead to the identification of proteins with novel antimicrobial properties.
| S-EPMC9134191 | biostudies-literature
Project description:PurposeThe type VI system (T6SS) has the potential to be a new virulence factor for hypervirulent Klebsiella pneumoniae (hvKp) strains. This study aimed to characterize the molecular and clinical features of T6SS-positive and T6SS-negative K. pneumoniae isolates that cause abscesses.Patients and methodsA total of 169 non-duplicate K. pneumoniae strains were isolated from patients with abscesses in a tertiary hospital in China from January 2018 to June 2022, and clinical data were collected. For all isolates, capsular serotypes, T6SS genes, virulence, and drug resistance genes, antimicrobial susceptibility testing, and biofilm formation assays were assessed. Multilocus sequence typing was used to analyze the genotypes of hvKp. T6SS-positive hvKp, T6SS-negative hvKp, T6SS-positive cKP, and T6SS-negative cKP (n = 4 strains for each group) were chosen for the in vivo Galleria mellonella infection model and in vitro competition experiments to further explore the microbiological characteristics of T6SS-positive K. pneumoniae isolates.ResultsThe positive detection rate for T6SS was 36.1%. The rates of hvKp, seven virulence genes, K1 capsular serotype, and ST23 in T6SS-positive strains were all higher than those in T6SS-negative strains (p < 0.05). Multivariate logistic regression analysis indicated that the carriage of aerobactin (OR 0.01) and wcaG (OR 33.53) were independent risk factors for T6SS-positive strains (p < 0.05). The T6SS-positive strains had a stronger biofilm-forming ability than T6SS-negative strains (p < 0.05). The T6SS-positive and T6SS-negative strains showed no significant differences in competitive ability (p = 0.06). In the in vivo G. mellonella infection model, the T6SS(+)/hvKP group had the worst prognosis. Except for cefazolin and tegacyclin, T6SS-positive isolates displayed a lower rate of antimicrobial resistance to other drugs (p < 0.05). The T6SS-positive isolates were more likely to be acquired from community infections (p < 0.05).ConclusionKlebsiella pneumoniae isolates causing abscesses have a high prevalence of T6SS genes. T6SS-positive K. pneumoniae isolates are associated with virulence, and the T6SS genes may be involved in the hvKp virulence mechanism.
| S-EPMC10230222 | biostudies-literature
Project description:Klebsiella pneumoniae, a pathogen of critical clinical concern, urgently demands effective therapeutic options owing to its drug resistance. Polymyxins are increasingly regarded as a last-line therapeutic option for the treatment of multidrug-resistant (MDR) Gram-negative bacterial infections. However, polymyxin resistance in K. pneumoniae is an emerging issue. Here, we report that gallium nitrate (GaNt), an antimicrobial candidate, exhibits a potentiating effect on colistin against MDR K. pneumoniae clinical isolates. To further confirm this, we investigated the efficacy of combined GaNt and colistin in vitro using spot dilution and rapid time-kill assays and growth curve inhibition tests and in vivo using a murine lung infection model. The results showed that GaNt significantly increased the antimicrobial activity of colistin, especially in the iron-limiting media. Mechanistic studies demonstrated that bacterial antioxidant activity was repressed by GaNt, as revealed by RNA sequencing (RNA-seq), leading to intracellular accumulation of reactive oxygen species (ROS) in K. pneumoniae, which was enhanced in the presence of colistin. Therefore, oxidative stress induced by GaNt and colistin augments the colistin-mediated killing of wild-type cells, which can be abolished by dimethyl sulfoxide (DMSO), an effective ROS scavenger. Collectively, our study indicates that GaNt has a notable impact on the antimicrobial activity of colistin against K. pneumoniae, revealing the potential of GaNt as a novel colistin adjuvant to improve the treatment outcomes of bacterial infections. IMPORTANCE This study aimed to determine the antimicrobial activity of GaNt combined with colistin against Klebsiella pneumoniae in vitro and in vivo. Our results suggest that by combining GaNt with colistin, antioxidant activity was suppressed and reactive oxygen species accumulation was induced in bacterial cells, enhancing antimicrobial activity against K. pneumoniae. We found that GaNt functioned as an antibiotic adjuvant when combined with colistin by inhibiting the growth of multidrug-resistant K. pneumoniae. Our study provides insight into the use of an adjuvant to boost the antibiotic potential of colistin for treating infections caused by multidrug-resistant K. pneumoniae.
| S-EPMC10434156 | biostudies-literature
Project description:Paraburkholderia phymatum STM815, a rhizobial strain of the Burkholderiaceae family, is able to nodulate a broad range of legumes including the agriculturally important Phaseolus vulgaris (common bean). P. phymatum harbors two type VI Secretion Systems (T6SS-b and T6SS-3) in its genome that contribute to its high interbacterial competitiveness in vitro and in infecting the roots of several legumes. In this study, we show that P. phymatum T6SS-b is found in the genomes of several soil-dwelling plant symbionts and that its expression is induced by the presence of citrate and is higher at 20/28°C compared to 37°C. Conversely, T6SS-3 shows homologies to T6SS clusters found in several pathogenic Burkholderia strains, is more prominently expressed with succinate during stationary phase and at 37°C. In addition, T6SS-b expression was activated in the presence of germinated seeds as well as in P. vulgaris and Mimosa pudica root nodules. Phenotypic analysis of selected deletion mutant strains suggested a role of T6SS-b in motility but not at later stages of the interaction with legumes. In contrast, the T6SS-3 mutant was not affected in any of the free-living and symbiotic phenotypes examined. Thus, P. phymatum T6SS-b is potentially important for the early infection step in the symbiosis with legumes.
| S-EPMC8356804 | biostudies-literature
Project description:The type VI secretion system (T6SS) is a class of sophisticated cell contact-dependent apparatus with anti-eukaryotic or anti-bacterial function. Klebsiella pneumoniae is one of the most common bacterial pathogens with resistance to the carbapenem antibiotics. However, little is known about the antibacterial T6SS in K. pneumoniae. Using core-component protein searches, we identified a putative T6SS gene cluster on the chromosome of the carbapenemase-producing K. pneumoniae (CRKP) strain HS11286. Intraspecies and interspecies competition assays revealed an antibacterial function of the HS11286 T6SS. The phospholipase Tle1KP was found to be an effector protein that is transferred by T6SS. The overexpression of this effector gene in the periplasm caused severe growth inhibition of Escherichia coli. A sub-inhibitory concentration of β-lactam antibiotics stimulated the expression and secretion of the HS11286 T6SS and enhanced T6SS-dependent killing. It suggested that the antibiotics might be an impact factor for the T6SS secretion and antibacterial activity.
| S-EPMC5649205 | biostudies-literature
Project description:Burkholderia cenocepacia is an opportunistic bacterial pathogen that poses a significant threat to individuals with cystic fibrosis by provoking a strong inflammatory response within the lung. It possesses a type VI secretion system (T6SS), a secretory apparatus that can perforate the cellular membrane of other bacterial species and/or eukaryotic targets, to deliver an arsenal of effector proteins. The B. cenocepacia T6SS (T6SS-1) has been shown to be implicated in virulence in rats and contributes toward actin rearrangements and inflammasome activation in B. cenocepacia-infected macrophages. Here, we present bioinformatics evidence to suggest that T6SS-1 is the archetype T6SS in the Burkholderia genus. We show that B. cenocepacia T6SS-1 is active under normal laboratory growth conditions and displays antibacterial activity against other Gram-negative bacterial species. Moreover, B. cenocepacia T6SS-1 is not required for virulence in three eukaryotic infection models. Bioinformatics analysis identified several candidate T6SS-dependent effectors that may play a role in the antibacterial activity of B. cenocepacia T6SS-1. We conclude that B. cenocepacia T6SS-1 plays an important role in bacterial competition for this organism, and probably in all Burkholderia species that possess this system, thereby broadening the range of species that utilize the T6SS for this purpose.
| S-EPMC6612558 | biostudies-literature
Project description:Type VI secretion systems (T6SS) are a class of macromolecular secretion machines that are utilized by a number of bacteria for inter-bacterial competition or to elicit responses in eukaryotic cells. Acinetobacter baumannii is an opportunistic pathogen that causes severe infections in humans. These infections, including pneumonia and bacteremia, are important, as they are often associated with hospitals and medical-settings where they disproportionally affect critically ill patients like those residing in intensive care units. While it is known that A. baumannii genomes carry genes whose predicted products have homology with T6SS-associated gene products from other bacteria, and secretion of a major T6SS structural protein Hcp has been demonstrated, no additional work on an A. baumannii T6SS has been reported. Herein, we demonstrated that A. baumannii strain M2 secretes Hcp and this secretion was dependent upon TssB, an ortholog of a bacteriophage contractile sheath protein, confirming that strain M2 produces a functional T6SS. Additionally, we demonstrated that the ability of strain M2 to out-compete Escherichia coli was reliant upon the products of tssB and hcp. Collectively, our data have provided the first evidence demonstrating function in inter-bacterial competition, for a T6SS produced by A. baumannii.
| S-EPMC3602014 | biostudies-literature