Biology subjects

Crisan, C.

Publications and source records attributed to Crisan, C..

4 recordsLinked to original sources

bioRxiv2023

The Type VI Secretion System of the Emerging Pathogen Stenotrophomonas maltophilia has Antibacterial Properties

Antagonistic behaviors between bacterial cells can have profound effects on microbial populations and disease outcomes. Polymicrobial interactions may be mediated by contact-dependent proteins with antibacterial properties. The Type VI Secretion System (T6SS) is a macromolecular weapon used by Gram-negative bacteria to translocate proteins into adjacent cells. The T6SS is used by pathogens to escape immune cells, eliminate commensal bacteria, and facilitate infection. Stenotrophomonas maltophilia is a Gram-negative opportunistic pathogen that causes a wide range of infections in immunocompromised patients and infects the lungs of patients with cystic fibrosis. Infections with the bacterium can be deadly and are challenging to treat because many isolates are multidrug-resistant. We found that globally dispersed S. maltophilia clinical and environmental strains possess T6SS genes. We demonstrate that the T6SS of an S. maltophilia patient isolate is active and can eliminate other bacteria. Furthermore, we provide evidence that the T6SS contributes to the competitive fitness of S. maltophilia against a co-infecting Pseudomonas aeruginosa isolate, and that the T6SS alters the cellular organization of S. maltophilia and P. aeruginosa co-cultures. This study expands our knowledge of the mechanisms employed by S. maltophilia to secrete antibacterial proteins and compete against other bacteria. IMPORTANCEInfections with the opportunistic pathogen Stenotrophomonas maltophilia can be fatal for immunocompromised patients. The mechanisms used by the bacterium to compete against other prokaryotes are not well understood. We found that the T6SS allows S. maltophilia to eliminate other bacteria and contributes to the competitive fitness against a co-infecting isolate. The presence of T6SS genes in isolates across the globe highlights the importance of this apparatus as a weapon in the antibacterial arsenal of S. maltophilia. The T6SS may confer survival advantages to S. maltophilia isolates in polymicrobial communities in both environmental settings and during infections.

microbiology↗

bioRxiv2021

A new contact killing toxin permeabilizes cells and belongs to a large protein family

Vibrio cholerae is an aquatic Gram-negative bacterium that causes severe diarrheal cholera disease when ingested by humans. To eliminate competitor cells in both the external environment and inside hosts, V. cholerae uses the Type VI Secretion System (T6SS). The T6SS is a macromolecular weapon employed by many Gram-negative bacteria to deliver cytotoxic proteins into adjacent cells. In addition to canonical T6SS gene clusters encoded by all sequenced V. cholerae isolates, strain BGT49 encodes an additional locus, which we named auxiliary cluster 4 (Aux 4). The Aux 4 cluster is located on a mobile genetic element and can be used by killer cells to eliminate both V. cholerae and Escherichia coli cells in a T6SS-dependent manner. A putative toxin encoded in the cluster, which we name TpeV (Type VI Permeabilizing Effector Vibrio), shares no homology to known proteins and does not contain motifs or domains indicative of function. Ectopic expression of TpeV in the periplasm of E. coli permeabilizes cells and disrupts the membrane potential. Using confocal microscopy, we confirm that susceptible target cells become permeabilized when competed with killer cells harboring the Aux 4 cluster. We also determine that tpiV, the gene located immediately downstream of tpeV, encodes an immunity protein that neutralizes the toxicity of TpeV. Finally, we show that TpeV homologs are broadly distributed across important animal and plant pathogens and are localized in proximity to other T6SS genes. Our results suggest that TpeV is a toxin that belongs to a large family of T6SS proteins. IMPORTANCEBacteria live in polymicrobial communities where competition for resources and space is essential for survival. Proteobacteria use the T6SS to eliminate neighboring cells and cause disease. However, the mechanisms by which many T6SS toxins kill or inhibit susceptible target cells are poorly understood. The sequence of the TpeV toxin we describe here is unlike any previously described protein. We demonstrate that it has antimicrobial activity by permeabilizing cells, eliminating membrane potentials and causing severe cytotoxicity. TpeV homologs are found near known T6SS genes in human, animal and plant bacterial pathogens, indicating that the toxin is a representative member of a broadly distributed protein family. We propose that TpeV-like toxins contribute to the fitness and pathogenicity of many bacteria. Finally, since antibiotic resistance is a critical global health threat, the discovery of new antimicrobial mechanisms could lead to the development of new treatments against resistant strains.

microbiology↗

bioRxiv2020

Glucose promotes resistance of human commensal Escherichia coli against contact-killing by pandemic Vibrio cholerae

Evolutionary arms races among organisms are broadly prevalent and bacteria have evolved defensive strategies against various attackers. A common microbial aggression mechanism is the Type VI Secretion System (T6SS), a contact-dependent bacterial weapon used to deliver toxic effector proteins into adjacent target cells. Sibling cells constitutively express immunity proteins that neutralize effectors. However, less is known about mechanisms that allow non-sibling bacteria to respond to external cues and survive T6SS attacks independently of immunity proteins. In this study, we show that resistance to T6SS attacks is promoted by a genetically controlled response to exogenous glucose. We observe that multiple human Escherichia coli commensal strains lacking immunity proteins are sensitive to T6SS attacks from pandemic Vibrio cholerae on nutrient-rich media. By contrast, E. coli cells become resistant to attacks when co-cultured on the same media with glucose. We confirm that glucose does not impair V. cholerae T6SS activity. Instead, we find that cAMP receptor protein (CRP), which alters expression of hundreds of genes in response to glucose, controls resistance to T6SS attacks in E. coli cells. Consistent with the observed resistance on media with glucose, an E. coli crp disruption mutant survives significantly better against V. cholerae T6SS attacks even in the absence of glucose. Finally, we also show that resistance to T6SS attacks depends on the pH of the medium and varies based on the target and killer strains. IMPORTANCEMany Gram-negative bacteria, including important pathogens, encode T6SS genes to deliver toxic effectors and eliminate competitors. Our results uncover a novel defense mechanism against T6SS attacks that is triggered by an external stimulus and mediated by a metabolic response in non-kin target cells. In microbiomes such as those in gastrointestinal tracts where T6SS activity is known to occur, signaling by metabolites like glucose may affect the efficacy of T6SS attacks and alter microbial community composition. Our findings could have vast implications for microbial interactions during pathogen colonization of hosts and survival of bacterial cells in environmental communities. Furthermore, the glucose-mediated resistance observed here might provide a novel example of an evolutionary arms race between killer T6SS cells and target bacteria.

microbiology↗

bioRxiv2019

Efficacy and safety of a novel vaginal medical device in Recurrent Bacterial Vaginosis: an international multicentre clinical trial

Several risk factors have been identified but the etiology and pathogenesis of Bacterial vaginosis (BV) are still not completely understood, and the recurrence rate of BV remains high despite adequate chemotherapy treatment. The primary objective of the study was to assess the effectiveness of a new vaginal medical device, which contains polycarbophil, 0.04 % lauryl glucoside, and glycerides (Polybactum(R) - Effik Italia), in reducing BV recurrence rate. This was a multicenter, open label, not comparative study performed in Italy and Romania. Female subjects over 18-years-old affected by recurrent BV were included. The latest episode was diagnosed by Amsel criteria 6-9 days before the start of the study and treated with vaginal metronidazole (gel 0.75% mg for 5 days or ovules 500 mg for 7 days). The recurrence was defined by at least 2 episodes in the previous 12 months. Polybactum(R) vaginal ovules, day 1-4-7, were started within the 12th and the 24th hr after the end of metronidazole therapy and repeated monthly for 3 cycles. The first 41 patients enrolled were evaluated for an interim analysis 6 months after the study started; 2 patients interrupted the trial, leaving 39 evaluable subjects. The recurrence rate was significantly reduced compared to previous published data (10.26% vs 40% p<0.001). In 35 patients without recurrence, the assessment of Lactobacillus vaginal flora performed by phase contrast microscopy evidenced a significant improvement form baseline (p=0.022) The Investigator global assessment of tolerability was excellent in 38 out of 39 cases. IMPORTANCEBacterial vaginosis (BV) is the most common vaginal disorder in women of childbearing age. In BV, Lactobacillus species, which are predominant in a healthy vaginal flora, are replaced by anaerobes, mainly Gardnerella vaginalis. BV is responsible for more than 60% of vulvovaginal infections and has been linked to serious, potentially life-threatening conditions, including: pelvic inflammatory disease, postoperative infections, acquisition and transmission of the human immunodeficiency virus, preterm birth, and several adverse pregnancy outcomes. Our research showed that 3 monthly cycles of Polybactum(R) ovules administered after one course of metronidazole vaginal therapy can reduce the rate of Bacterial vaginosis recurrence and improve the vaginal milieu, favouring the growth of vaginal lactobacillus species. Taken together our results confirm that Polibactum(R) is a safe and effective treatment to reduce BV recurrence rate after a first line therapy with metronidazole.

clinical trials↗