Bacterial killing via a type IV secretion system

Souza, Diorge P.; Oka, Gabriel Umaji; Martı́nez, Consuelo; Bisson‐Filho, Alexandre W.; Dunger, Germán; Hobeika, Lise; Cavalcante, Nayara S.; Alegria, Marcos C.; Barbosa, Leandro R.S.; Salinas, Roberto Köpke; Guzzo, Cristiane R.; Farah, Chuck S.

doi:10.1038/ncomms7453

Cited by 205 publications

(280 citation statements)

References 70 publications

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“…Several effectors exert activity on both prokaryotic and eukaryotic cells. This challenges the assumed dichotomy expected from secretion machineries and their toxins, which has recently been supported by observations regarding the activity of the T4SS [66]. This emerging concept should be addressed upon future identification of T6SS effectors and applied to existing toxins where appropriate.…”

Section: Discussionmentioning

confidence: 92%

Type VI secretion and anti-host effectors

Hachani¹,

Wood

Filloux

2016

Current Opinion in Microbiology

233

194

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Secretion systems play a central role in infectious diseases by enabling pathogenic bacteria to deliver virulence factors into target cells. The type VI secretion system (T6SS) mediates bacterial antagonism in various environments including eukaryotic niches, such as the gut. This molecular machine injects lethal toxins directly in target bacterial cells. It provides an advantage to pathogens encountering the commensal flora of the host and indirectly contributes to colonization and persistence. Yet, the T6SS is not employed for the sole purpose of bacterial killing and several T6SS effectors are dedicated to the subversion of eukaryotic cells. As described for type III and type IV secretion systems, these effectors impede host cell functions and promote immune evasion, thereby enabling successful infection.

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Section: Discussionmentioning

confidence: 92%

Type VI secretion and anti-host effectors

Hachani¹,

Wood

Filloux

2016

Current Opinion in Microbiology

233

194

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“…10 The family Spirochaetaceae also was often abundant in viscera samples but absent in washes 11 ( Figure S2). 12 The number of taxa with low relative abundance could indicate that the internal 13 environment of I. scapularis is particularly well suited to fostering diverse microbial 14 communities. However, an alternate possibility is that low abundance OTUs represent signal 15 from contamination.…”

mentioning

confidence: 99%

Ixodes scapularisdoes not harbor a stable midgut microbiome

Ross

Hayes

Radey

et al. 2017

Preprint

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1Hard ticks of the order Ixodidae serve as vectors for numerous human pathogens, including the 2 causative agent of Lyme Disease Borrelia burgdorferi. Tick-associated microbes can influence 3 pathogen colonization, offering the potential to inhibit disease transmission through engineering 4 of the tick microbiota. Here, we investigate whether B. burgdorferi encounters abundant bacteria 5 within the midgut of wild adult Ixodes scapularis, its primary vector. Through the use of 6 controlled sequencing methods and confocal microscopy, we find that the majority of field-7 collected adult I. scapularis harbor limited internal microbial communities that are dominated by 8 endosymbionts. A minority of I. scapularis ticks harbor abundant midgut bacteria and lack B. 9 burgdorferi. We find that the lack of a stable resident midgut microbiota is not restricted to I. 10 scapularis since extension of our studies to I. pacificus, Amblyomma maculatum, and 11Dermacentor spp showed similar patterns. Finally, bioinformatic examination of the B. 12 burgdorferi genome revealed the absence of genes encoding known interbacterial interaction 13 pathways, a feature unique to the Borrelia genus within the phylum Spirochaetes. Our results 14 suggest that reduced selective pressure from limited microbial populations within ticks may have 15 facilitated the evolutionary loss of genes encoding interbacterial competition pathways from 16Borrelia.

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“…Because the Luteibacter genomes each assembled into one contig, it is likely that there were no plasmids present within these strains and therefore that the type IV secretion systems were encoded by the chromosome. We also note that a type IV system in Xanthomonas , closely related to Luteibacter , can be utilized to kill other bacterial strains [50]. In contrast, the genome sequence for the Rhizobium strain is split into seven distinct contigs, which is expected because related strains contain multiple secondary replicons [51].…”

Section: Resultsmentioning

confidence: 99%

Absence of genome reduction in diverse, facultative endohyphal bacteria

et al. 2017

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Fungi interact closely with bacteria, both on the surfaces of the hyphae and within their living tissues (i.e. endohyphal bacteria, EHB). These EHB can be obligate or facultative symbionts and can mediate diverse phenotypic traits in their hosts. Although EHB have been observed in many lineages of fungi, it remains unclear how widespread and general these associations are, and whether there are unifying ecological and genomic features can be found across EHB strains as a whole. We cultured 11 bacterial strains after they emerged from the hyphae of diverse Ascomycota that were isolated as foliar endophytes of cupressaceous trees, and generated nearly complete genome sequences for all. Unlike the genomes of largely obligate EHB, the genomes of these facultative EHB resembled those of closely related strains isolated from environmental sources. Although all analysed genomes encoded structures that could be used to interact with eukaryotic hosts, pathways previously implicated in maintenance and establishment of EHB symbiosis were not universally present across all strains. Independent isolation of two nearly identical pairs of strains from different classes of fungi, coupled with recent experimental evidence, suggests horizontal transfer of EHB across endophytic hosts. Given the potential for EHB to influence fungal phenotypes, these genomes could shed light on the mechanisms of plant growth promotion or stress mitigation by fungal endophytes during the symbiotic phase, as well as degradation of plant material during the saprotrophic phase. As such, these findings contribute to the illumination of a new dimension of functional biodiversity in fungi.

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Bacterial killing via a type IV secretion system

Cited by 205 publications

References 70 publications

Type VI secretion and anti-host effectors

Type VI secretion and anti-host effectors

Ixodes scapularisdoes not harbor a stable midgut microbiome

Absence of genome reduction in diverse, facultative endohyphal bacteria

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