Prevalence and Detailed Mapping of the Gonococcal Genetic Island in Neisseria meningitidis

Neisseria gonorrhoeae uses a type IV secretion system (T4SS) to secrete chromosomal DNA into the surrounding milieu. The DNA is effective in transforming gonococci in the population, and this mechanism of DNA donation may contribute to the high degree of genetic diversity in this species. Similar to other F-like T4SSs, the gonococcal T4SS requires a putative membrane protein, TraG, for DNA transfer. In F-plasmid and related systems, the homologous protein acts in pilus production, mating pair stabilization, and entry exclusion. We characterized the localization, membrane topology, and variation of TraG in N. gonorrhoeae. TraG was found to be an inner-membrane protein with one large periplasmic region and one large cytoplasmic region. Each gonococcal strain carried one of three different alleles of traG. Strains that carried the smallest allele of traG were found to lack the peptidoglycanase gene atlA but carried a peptidoglycan endopeptidase gene in place of atlA. The purified endopeptidase degraded gonococcal peptidoglycan in vitro, cutting the peptide cross-links. Although the other two traG alleles functioned for DNA secretion in strain MS11, the smallest traG did not support DNA secretion. Despite the requirement for a mating pair stabilization homologue, static coculture transformation experiments demonstrated that DNA transfer was nuclease sensitive and required active uptake by the recipient, thus demonstrating that transfer occurred by transformation and not conjugation. Together, these results demonstrate the TraG acts in a process of DNA export not specific to conjugation and that different forms of TraG affect what substrates can be transported.

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“…Furthermore, all meningococcal strains that carry the GGI and have the traG region, have the traG3 allele and eppA (45).…”

Section: Discussionmentioning

confidence: 99%

“…We sequenced the traG region in this strain and found sequences similar to traG3 and eppA of strain PID2059. To date, all N. meningitidis strains that carry the GGI and a traG allele, have traG3 and eppA (45).…”

Section: Fig 4 (A) Southern Blot Analysis Of Ecori-and Clai-digested mentioning

confidence: 99%

Mating Pair Formation Homologue TraG Is a Variable Membrane Protein Essential for Contact-Independent Type IV Secretion of Chromosomal DNA by Neisseria gonorrhoeae

et al. 2013

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“…For DNA-secreting gonococci, it was suggested that homologs of ParA and ParB might bind to DNA and bring it to the type IV secretion machinery (T4SS), where it is further processed by a relaxase and a helicase before it is secreted as ssDNA (58,59). Interestingly, deletion mutants of ParA or ParB in Neisseria gonorrhoeae indeed showed strongly reduced DNA secretion (60,61).…”

Section: Figmentioning

confidence: 99%

DNA Processing Proteins Involved in the UV-Induced Stress Response of Sulfolobales

Wolferen

Albers

2015

J Bacteriol

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The ups operon of Sulfolobus species is highly induced upon UV stress. Previous studies showed that the pili encoded by this operon are involved in cellular aggregation, which is essential for subsequent DNA exchange between cells, resulting in homologous recombination. The presence of this pilus system increases the fitness of Sulfolobus cells under UV light-induced stress conditions, as the transfer of DNA takes place in order to repair UV-induced DNA lesions via homologous recombination. Four conserved genes (saci_1497 to saci_1500) which encode proteins with putative DNA processing functions are present downstream of the ups operon. In this study, we show that after UV treatment the cellular aggregation of strains with saci_1497, saci_1498, and saci_1500 deletions is similar to that of wild-type strains; their survival rates, however, were reduced and similar to or lower than those of the pilus deletion strains, which could not aggregate anymore. DNA recombination assays indicated that saci_1498, encoding a ParB-like protein, plays an important role in DNA transfer. Moreover, biochemical analysis showed that the endonuclease III encoded by saci_1497 nicks UV-damaged DNA. In addition, RecQ-like helicase Saci_1500 is able to unwind homologous recombination intermediates, such as Holliday junctions. Interestingly, a saci_1500 deletion mutant was more sensitive to UV light but not to the replication-stalling agents hydroxyurea and methyl methanesulfonate, suggesting that Saci_1500 functions specifically in the UV damage pathway. Together these results suggest a role of Saci_1497 to Saci_1500 in the repair or transfer of DNA that takes place after UV-induced damage to the genomic DNA of Sulfolobus acidocaldarius. IMPORTANCESulfolobales species increase their fitness after UV stress by a UV-inducible pilus system that enables high rates of DNA exchange between cells. Downstream of the pilus operon, three genes that seem to play a role in the repair or transfer of the DNA between Sulfolobus cells were identified, and their possible functions are discussed. Next to the previously described role of UV-inducible pili in the exchange of DNA, we have thereby increased our knowledge of DNA transfer at the level of DNA processing. This paper therefore contributes to the overall understanding of the DNA exchange mechanism among Sulfolobales cells. In all domains of life, DNA repair is crucial for maintenance of genome integrity upon exposure to intra-or extracellular DNAdamaging threats (1). Unlike DNA repair in bacteria, archaeal DNA repair and its regulation are still far from well understood (1, 2). Homology searches revealed that the proteins in archaeal DNA repair pathways show similarities to both bacterial and eukaryotic proteins. In addition, DNA repair proteins with unique archaeal features exist (3).Previously, it was speculated that archaea might have SOS-like responses similar to those in certain bacteria (4); however, microarray studies revealed that neither Haloarchaea (5, 6) nor Sulfolobus species (7...

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“…The transformation process has been well described for some species, such as Streptococcus pneumoniae, Vibrio cholerae, Neisseria meningitidis, and Helicobacter pylori (8)(9)(10)(11)(12). However, how natural competence is regulated has not been thoroughly studied, particularly for Gram-negative bacteria.…”

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Serum Albumin and Ca ²⁺ Are Natural Competence Inducers in the Human Pathogen Acinetobacter baumannii

Traglia

Quinn

Schramm

et al. 2016

Antimicrob Agents Chemother

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The increasing frequency of bacteria showing antimicrobial resistance (AMR) raises the menace of entering into a postantibiotic era. Horizontal gene transfer (HGT) is one of the prime reasons for AMR acquisition. Acinetobacter baumannii is a nosocomial pathogen with outstanding abilities to survive in the hospital environment and to acquire resistance determinants. Its capacity to incorporate exogenous DNA is a major source of AMR genes; however, few studies have addressed this subject. The transformation machinery as well as the factors that induce natural competence in A. baumannii are unknown. In this study, we demonstrate that naturally competent strain A118 increases its natural transformation frequency upon the addition of Ca 2؉ or albumin. We show that comEA and pilQ are involved in this process since their expression levels are increased upon the addition of these compounds. An unspecific protein, like casein, does not reproduce this effect, showing that albumin's effect is specific. Our work describes the first specific inducers of natural competence in A. baumannii. Overall, our results suggest that the main protein in blood enhances HGT in A. baumannii, contributing to the increase of AMR in this threatening human pathogen.A cinetobacter baumannii has emerged as a severe nosocomial pathogen over the course of the last few decades, with high levels of morbidity and mortality associated with infections by this pathogen (1, 2). A. baumannii is considered to be a paradigm of multidrug resistance since it has developed resistance to almost all available antibiotics, leaving few or no treatment options left. The ability of A. baumannii to persist in the clinical setting even under desiccation and nutrient starvation, as well as its ability to accumulate several antibiotic resistance determinants, allowed its evolution as a successful pathogen in the hospital environment (3).The large number of available A. baumannii genomes (n ϭ 1,289) shows that foreign DNA is acquired at high frequencies (4-7).The transformation process has been well described for some species, such as Streptococcus pneumoniae, Vibrio cholerae, Neisseria meningitidis, and Helicobacter pylori (8-12). However, how natural competence is regulated has not been thoroughly studied, particularly for Gram-negative bacteria. Some well-characterized competence inducers are DNA damage in H. pylori (13), starvation, as was suggested for Haemophilus influenzae, and chitin metabolism in Vibrio cholerae (14,15). In most known examples, natural competence is a transitory state that is regulated by different internal and external signals. Often, these regulation networks are not completely understood. For Acinetobacter spp., most of the studies focusing on this issue were performed by using Acinetobacter baylyi strain ADP1 (16-20), a bacterium not as threatening to human health as A. baumannii (18-23). Data regarding A. baumannii and competence inducers are scarce (24-27). Wilharm et al. showed previously that several A. baumannii clinical isolates were a...

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Prevalence and Detailed Mapping of the Gonococcal Genetic Island in Neisseria meningitidis

Cited by 32 publications

References 37 publications

Mating Pair Formation Homologue TraG Is a Variable Membrane Protein Essential for Contact-Independent Type IV Secretion of Chromosomal DNA by Neisseria gonorrhoeae

Mating Pair Formation Homologue TraG Is a Variable Membrane Protein Essential for Contact-Independent Type IV Secretion of Chromosomal DNA by Neisseria gonorrhoeae

DNA Processing Proteins Involved in the UV-Induced Stress Response of Sulfolobales

Serum Albumin and Ca ²⁺ Are Natural Competence Inducers in the Human Pathogen Acinetobacter baumannii

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Prevalence and Detailed Mapping of the Gonococcal Genetic Island in Neisseria meningitidis

Cited by 32 publications

References 37 publications

Mating Pair Formation Homologue TraG Is a Variable Membrane Protein Essential for Contact-Independent Type IV Secretion of Chromosomal DNA by Neisseria gonorrhoeae

Mating Pair Formation Homologue TraG Is a Variable Membrane Protein Essential for Contact-Independent Type IV Secretion of Chromosomal DNA by Neisseria gonorrhoeae

DNA Processing Proteins Involved in the UV-Induced Stress Response of Sulfolobales

Serum Albumin and Ca 2+ Are Natural Competence Inducers in the Human Pathogen Acinetobacter baumannii

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Serum Albumin and Ca ²⁺ Are Natural Competence Inducers in the Human Pathogen Acinetobacter baumannii