scholarly journals A competence-regulated toxin-antitoxin system inHaemophilus influenzae

2019 ◽  
Author(s):  
Hailey Findlay Black ◽  
Scott Mastromatteo ◽  
Sunita Sinha ◽  
Rachel L. Ehrlich ◽  
Corey Nislow ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Haemophilus Influenzae ◽  
Gene Pair ◽  
Carbon Sources ◽  
Toxin Gene ◽  
Dna Uptake ◽  
Rna Seq ◽  
Putative Toxin ◽  
Species Deletion

ABSTRACTNatural competence allows bacteria to respond to environmental and nutritional cues by taking up free DNA from their surroundings, thus gaining both nutrients and genetic information. In the Gram-negative bacteriumHaemophilus influenzae, the genes needed for DNA uptake are induced by the CRP andSxytranscription factors in response to lack of preferred carbon sources and nucleotide precursors. Here we show that one of these genes,HI0659, encodes the antitoxin of a competence-regulated toxin-antitoxin operon (‘toxTA’), likely acquired by horizontal gene transfer from aStreptococcusspecies. Deletion of the putative toxin(HI0660)restores uptake to the antitoxin mutant. The fulltoxTAoperon was present in only 17 of the 181 strains we examined; complete deletion was seen in 22 strains and deletions removing parts of the toxin gene in 142 others. In addition to the expected Sxy-and CRP-dependent-competence promoter,HI0659/660transcript analysis using RNA-seq identified an internal antitoxin-repressed promoter whose transcription starts withintoxTand will yield nonfunctional protein. We propose that the most likely effect of unopposed toxin expression is non-specific cleavage of mRNAs and arrest or death of competent cells in the culture. Although the high frequency oftoxTandtoxTAdeletions suggests that this competence-regulated toxin-antitoxin system may be mildly deleterious, it could also facilitate downregulation of protein synthesis and recycling of nucleotides under starvation conditions. Although our analyses were focused on the effects oftoxTA, the RNA-seq dataset will be a useful resource for further investigations into competence regulation.ABBREVIATED SUMMARYThe competence regulon ofHaemophilus influenzaeincludes an unprecedented toxin/antitoxin gene pair. When not opposed by antitoxin, the toxin completely prevents DNA uptake but causes only very minor decreases in cell growth and competence gene expression. The TA gene pair was acquired by horizontal gene transfer, and the toxin gene has undergone repeated deletions in other strains.

scholarly journals A competence-regulated toxin-antitoxin system in Haemophilus influenzae

2018 ◽  
Author(s):  
Hailey Findlay Black ◽  
Scott Mastromatteo ◽  
Sunita Sinha ◽  
Rachel L. Ehrlich ◽  
Corey Nislow ◽  
...  
Keyword(s):  
Genetic Information ◽  
Carbon Sources ◽  
Toxin Gene ◽  
Dna Uptake ◽  
Transcript Analysis ◽  
Rna Seq ◽  
Negative Bacterium ◽  
Natural Competence ◽  
Starvation Conditions ◽  
Species Deletion

ABSTRACTNatural competence allows bacteria to respond to environmental and nutritional cues by taking up free DNA from their surroundings, thus gaining nutrients and genetic information. In the Gram-negative bacterium Haemophilus influenae, the DNA uptake machinery is induced by the CRP and Sxy transcription factors in response to lack of preferred carbon sources and nucleotide precursors. Here we show that HI0659—which is absolutely required for DNA uptake— encodes the antitoxin of a competence-regulated toxin-antitoxin operon (‘toxTA’), likely acquired by horizontal gene transfer from a Streptococcus species. Deletion of the toxin restores uptake to the antitoxin mutant. In addition to the expected Sxy-and CRP-dependent-competence promoter, transcript analysis using RNA-seq identified an internal antitoxin-repressed promoter whose transcription starts within toxT and will yield nonfunctional protein. We present evidence that the most likely effect of unopposed toxin expression is non-specific cleavage of mRNAs and arrest or death of competent cells in the culture, and we show that the toxin gene has been inactivated by deletion in many H. influenzae strains. We suggest that this competence-regulated toxin-antitoxin system may facilitate downregulation of protein synthesis and recycling of nucleotides under starvation conditions, or alternatively be a simple genetic parasite.

scholarly journals Horizontal gene transfer of a bacterial insect toxin gene into the Epichloë fungal symbionts of grasses

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Karen V. Ambrose ◽  
Albrecht M. Koppenhöfer ◽  
Faith C. Belanger
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Toxin Gene ◽  
Insect Toxin

scholarly journals Repression of YdaS Toxin is Mediated by Transcriptional Repressor RacR in the cryptic rac prophage of Escherichia coli-K12

2017 ◽  
Author(s):  
Revathy Krishnamurthi ◽  
Swagatha Ghosh ◽  
Supriya Khedkar ◽  
Aswin Sai Narain Seshasayee
Keyword(s):  
Escherichia Coli ◽  
Transcription Factor ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Driving Force ◽  
Transcriptional Repressor ◽  
Genomic Diversity ◽  
Toxin Gene ◽  
Escherichia Coli K12 ◽  
Putative Transcription Factor

AbstractHorizontal gene transfer is a major driving force behind the genomic diversity seen in prokaryotes. Theracprophage inE.coliK12 encodes a putative transcription factor RacR, whose deletion is lethal. We have shown that the essentiality ofracRinE.coliK12 is attributed to its role in transcriptionally repressing a toxin gene calledydaS, which is coded adjacent and divergently toracR.

scholarly journals Role of Horizontal Gene Transfer in the Development of Multidrug Resistance in Haemophilus influenzae

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Kristin Hegstad ◽  
Haima Mylvaganam ◽  
Jessin Janice ◽  
Ellen Josefsen ◽  
Audun Sivertsen ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Haemophilus Influenzae ◽  
Resistance Genes ◽  
Mobile Genetic Elements ◽  
Beta Lactam ◽  
Content Type ◽  
Genetic Elements ◽  
Wide Range ◽  
Chromosomal Genes

ABSTRACT Haemophilus influenzae colonizes the respiratory tract in humans and causes both invasive and noninvasive infections. Resistance to extended-spectrum cephalosporins in H. influenzae is rare in Europe. In this study, we defined acquired resistance gene loci and ftsI mutations in multidrug-resistant (MDR) and/or PBP3-mediated beta-lactam-resistant (rPBP3) H. influenzae strains, intending to understand the mode of spread of antibiotic resistance determinants in this species. Horizontal transfer of mobile genetic elements and transformation with resistance-conferring ftsI alleles were contributory. We found one small plasmid and three novel integrative conjugative elements (ICEs) which carry different combinations of resistance genes. Demonstration of transfer and/or ICE circular forms showed that the ICEs are functional. Two extensively MDR genetically unrelated H. influenzae strains (F and G) from the same geographical region shared an identical novel MDR ICE (Tn6686) harboring blaTEM-1, catA2-like, and tet(B). The first Nordic case of MDR H. influenzae septicemia, strain 0, originating from the same geographical area as these strains, had a similar resistance pattern but contained another ICE [Tn6687 with blaTEM-1, catP and tet(B)] with an overall structure quite similar to that of Tn6686. Comparison of the complete ftsI genes among rPBP3 strains revealed that the entire gene or certain regions of it are identical in genetically unrelated strains, indicating horizontal gene transfer. Our findings illustrate that H. influenzae is capable of acquiring resistance against a wide range of commonly used antibiotics through horizontal gene transfer, in terms of conjugative transfer of ICEs and transformation of chromosomal genes. IMPORTANCE Haemophilus influenzae colonizes the respiratory tract in humans and causes both invasive and noninvasive infections. As a threat to treatment, resistance against critically important antibiotics is on the rise in H. influenzae. Identifying mechanisms for horizontal acquisition of resistance genes is important to understand how multidrug resistance develops. The present study explores the antimicrobial resistance genes and their context in beta-lactam-resistant H. influenzae with coresistance to up to four non-beta-lactam groups. The results reveal that this organism is capable of acquiring resistance to a wide range of commonly used antibiotics through conjugative transfer of mobile genetic elements and transformation of chromosomal genes, resulting in mosaic genes with a broader resistance spectrum. Strains with chromosomally mediated resistance to extended-spectrum cephalosporins, co-trimoxazole, and quinolones combined with mobile genetic elements carrying genes mediating resistance to ampicillin, tetracyclines, and chloramphenicol have been reported, and further dissemination of such strains represents a particular concern.

scholarly journals Direct Visualization of Horizontal Gene Transfer by Transformation in Live Pneumococcal Cells Using Microfluidics

Genes ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 675
Author(s):  
Isabelle Mortier-Barrière ◽  
Patrice Polard ◽  
Nathalie Campo
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Expression Profiles ◽  
Physiological State ◽  
Microfluidic System ◽  
Live Cells ◽  
Microfluidic Channels ◽  
Dna Uptake ◽  
Fluorescent Reporters ◽  
Natural Genetic Transformation

Natural genetic transformation is a programmed mechanism of horizontal gene transfer in bacteria. It requires the development of competence, a specialized physiological state during which proteins involved in DNA uptake and chromosomal integration are produced. In Streptococcus pneumoniae, competence is transient. It is controlled by a secreted peptide pheromone, the competence-stimulating peptide (CSP) that triggers the sequential transcription of two sets of genes termed early and late competence genes, respectively. Here, we used a microfluidic system with fluorescence microscopy to monitor pneumococcal competence development and transformation, in live cells at the single cell level. We present the conditions to grow this microaerophilic bacterium under continuous flow, with a similar doubling time as in batch liquid culture. We show that perfusion of CSP in the microfluidic chamber results in the same reduction of the growth rate of individual cells as observed in competent pneumococcal cultures. We also describe newly designed fluorescent reporters to distinguish the expression of competence genes with temporally distinct expression profiles. Finally, we exploit the microfluidic technology to inject both CSP and transforming DNA in the microfluidic channels and perform near real time-tracking of transformation in live cells. We show that this approach is well suited to investigating the onset of pneumococcal competence together with the appearance and the fate of transformants in individual cells.

scholarly journals Horizontal Gene Transfer of ftsI, Encoding Penicillin-Binding Protein 3, in Haemophilus influenzae

2007 ◽  
Vol 51 (5) ◽  
pp. 1589-1595 ◽  
Author(s):  
Sho Takahata ◽  
Takashi Ida ◽  
Nami Senju ◽  
Yumiko Sanbongi ◽  
Aiko Miyata ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Haemophilus Influenzae ◽  
Binding Protein ◽  
Resistant Mutant ◽  
Penicillin Binding Protein ◽  
Genetic Transfer ◽  
Complete Sequences

ABSTRACT Horizontal gene transfer has been identified in only a small number of genes in Haemophilus influenzae, an organism which is naturally competent for transformation. This report provides evidence for the genetic transfer of the ftsI gene, which encodes penicillin-binding protein 3, in H. influenzae. Mosaic structures of the ftsI gene were found in several clinical isolates of H. influenzae. To identify the origin of the mosaic sequence, complete sequences of the corresponding gene from seven type strains of Haemophilus species were determined. Comparison of these sequences with mosaic regions identified a homologous recombination of the ftsI gene between H. influenzae and Haemophilus haemolyticus. Subsequently, ampicillin-resistant H. influenzae strains harboring identical ftsI sequences were genotyped by pulsed-field gel electrophoresis (PFGE). Divergent PFGE patterns among β-lactamase-nonproducing ampicillin-resistant (BLNAR) strains from different hospitals indicated the potential for the genetic transfer of the mutated ftsI gene between these isolates. Moreover, transfer of the ftsI gene from BLNAR strains to β-lactamase-nonproducing ampicillin-susceptible (BLNAS) H. influenzae strains was evaluated in vitro. Coincubation of a BLNAS strain (a rifampin-resistant mutant of strain Rd) and BLNAR strains resulted in the emergence of rifampin- and cefdinir-resistant clones at frequencies of 5.1 × 10−7 to 1.5 × 10−6. Characterization of these doubly resistant mutants by DNA sequencing of the ftsI gene, susceptibility testing, and genotyping by PFGE revealed that the ftsI genes of BLNAR strains had transferred to BLNAS strains during coincubation. In conclusion, horizontal transfer of the ftsI gene in H. influenzae can occur in an intraspecies and an interspecies manner.

scholarly journals The capsule biosynthesis locus of Haemophilus influenzae shows conspicuous similarity to the corresponding locus in Haemophilus sputorum and may have been recruited from this species by horizontal gene transfer

Microbiology ◽  
2015 ◽  
Vol 161 (6) ◽  
pp. 1182-1188 ◽  
Author(s):  
Signe M. Nielsen ◽  
Lars H. Hansen ◽  
Chrysoula Dimopoulou ◽  
Niels Nørskov-Lauritsen ◽  
Vikas Gupta ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Haemophilus Influenzae

scholarly journals Horizontal gene transfer overrides mutation in Escherichia coli colonizing the mammalian gut

2019 ◽  
Vol 116 (36) ◽  
pp. 17906-17915 ◽  
Author(s):  
Nelson Frazão ◽  
Ana Sousa ◽  
Michael Lässig ◽  
Isabel Gordo
Keyword(s):  
Escherichia Coli ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Carbon Sources ◽  
Commensal Bacteria ◽  
Natural Environments ◽  
E Coli ◽  
Fitness Advantage ◽  
Gut Colonization ◽  
Mouse Intestine

Bacteria evolve by mutation accumulation in laboratory experiments, but tempo and mode of evolution in natural environments are largely unknown. Here, we study the ubiquitous natural process of host colonization by commensal bacteria. We show, by experimental evolution of Escherichia coli in the mouse intestine, that the ecology of the gut controls the pace and mode of evolution of a new invading bacterial strain. If a resident E. coli strain is present in the gut, the invading strain evolves by rapid horizontal gene transfer (HGT), which precedes and outweighs evolution by accumulation of mutations. HGT is driven by 2 bacteriophages carried by the resident strain, which cause an epidemic phage infection of the invader. These dynamics are followed by subsequent evolution by clonal interference of genetically diverse lineages of phage-carrying (lysogenic) bacteria. We show that the genes uptaken by HGT enhance the metabolism of specific gut carbon sources and provide a fitness advantage to lysogenic invader lineages. A minimal dynamical model explains the temporal pattern of phage epidemics and the complex evolutionary outcome of phage-mediated selection. We conclude that phage-driven HGT is a key eco-evolutionary driving force of gut colonization—it accelerates evolution and promotes genetic diversity of commensal bacteria.

scholarly journals A Conserved Metal Binding Motif in the Bacillus subtilis Competence Protein ComFA Enhances Transformation

2017 ◽  
Vol 199 (15) ◽  
Author(s):  
Scott S. Chilton ◽  
Tanya G. Falbel ◽  
Susan Hromada ◽  
Briana M. Burton
Keyword(s):  
Bacillus Subtilis ◽  
Amino Acid ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Metal Binding ◽  
Dna Uptake ◽  
Content Type ◽  
Efficient Transformation ◽  
Dead Box ◽  
The Dead

ABSTRACT Genetic competence is a process in which cells are able to take up DNA from their environment, resulting in horizontal gene transfer, a major mechanism for generating diversity in bacteria. Many bacteria carry homologs of the central DNA uptake machinery that has been well characterized in Bacillus subtilis. It has been postulated that the B. subtilis competence helicase ComFA belongs to the DEAD box family of helicases/translocases. Here, we made a series of mutants to analyze conserved amino acid motifs in several regions of B. subtilis ComFA. First, we confirmed that ComFA activity requires amino acid residues conserved among the DEAD box helicases, and second, we show that a zinc finger-like motif consisting of four cysteines is required for efficient transformation. Each cysteine in the motif is important, and mutation of at least two of the cysteines dramatically reduces transformation efficiency. Further, combining multiple cysteine mutations with the helicase mutations shows an additive phenotype. Our results suggest that the helicase and metal binding functions are two distinct activities important for ComFA function during transformation. IMPORTANCE ComFA is a highly conserved protein that has a role in DNA uptake during natural competence, a mechanism for horizontal gene transfer observed in many bacteria. Investigation of the details of the DNA uptake mechanism is important for understanding the ways in which bacteria gain new traits from their environment, such as drug resistance. To dissect the role of ComFA in the DNA uptake machinery, we introduced point mutations into several motifs in the protein sequence. We demonstrate that several amino acid motifs conserved among ComFA proteins are important for efficient transformation. This report is the first to demonstrate the functional requirement of an amino-terminal cysteine motif in ComFA.

scholarly journals Functional Analysis of PilT from the Toxic Cyanobacterium Microcystis aeruginosa PCC 7806

2006 ◽  
Vol 189 (5) ◽  
pp. 1689-1697 ◽  
Author(s):  
Kenlee Nakasugi ◽  
Ralitza Alexova ◽  
Charles J. Svenson ◽  
Brett A. Neilan
Keyword(s):  
Gene Transfer ◽  
Microcystis Aeruginosa ◽  
Structural Models ◽  
Toxin Gene ◽  
Dna Uptake ◽  
Type Iv Pilus ◽  
Type Iv ◽  
Critical Residues ◽  
Pcc 6803

ABSTRACT The evolution of the microcystin toxin gene cluster in phylogenetically distant cyanobacteria has been attributed to recombination, inactivation, and deletion events, although gene transfer may also be involved. Since the microcystin-producing Microcystis aeruginosa PCC 7806 is naturally transformable, we have initiated the characterization of its type IV pilus system, involved in DNA uptake in many bacteria, to provide a physiological focus for the influence of gene transfer in microcystin evolution. The type IV pilus genes pilA, pilB, pilC, and pilT were shown to be expressed in M. aeruginosa PCC 7806. The purified PilT protein yielded a maximal ATPase activity of 37.5 ± 1.8 nmol Pi min−1 mg protein−1, with a requirement for Mg2+. Heterologous expression indicated that it could complement the pilT mutant of Pseudomonas aeruginosa, but not that of the cyanobacterium Synechocystis sp. strain PCC 6803, which was unexpected. Differences in two critical residues between the M. aeruginosa PCC 7806 PilT (7806 PilT) and the Synechocystis sp. strain PCC 6803 PilT proteins affected their theoretical structural models, which may explain the nonfunctionality of 7806 PilT in its cyanobacterial counterpart. Screening of the pilT gene in toxic and nontoxic strains of Microcystis was also performed.

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