Stochastic activation of a family of TetR type transcriptional regulators controls phenotypic heterogeneity in <i>Acinetobacter baumannii</i>

Pérez-Varela, María; Tierney, Aimee R. P.; Dawson, Emma R.; Hutcheson, Anna R.; Tipton, Kyle A.; Anderson, Sarah E.; Haldopoulos, Marina E; Song, Shaina; Tomlinson, Brooke R.; Shaw, Lindsey N.; Weiss, David S.; Kim, Minsu; Rather, Philip N.

doi:10.1093/pnasnexus/pgac231

Cited by 9 publications

(20 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Tetracycline resistance is typically acquired through the activation of efflux pumps ( 18 , 19 ). The family of TetR-type transcriptional regulators is redundantly involved in driving this switching through uncharacterized molecular events ( 3 , 6 ). Strain AB5075 does not possess intrinsic resistance to tetracycline due to the absence of the tetRA cassette ( 20 ), despite having multiple copies of TetR-type transcriptional regulator-encoding genes.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Colony phase variation switch modulates antimicrobial tolerance and biofilm formation in Acinetobacter baumannii

Mushtaq,

Nadeem,

Yabrag

et al. 2024

Microbiol Spectr

View full text Add to dashboard Cite

Carbapenem-resistant Acinetobacter baumannii causes one of the most difficult-to-treat nosocomial infections. Polycationic drugs like polymyxin B or colistin and tetracycline drugs such as doxycycline or minocycline are commonly used to treat infections caused by carbapenem-resistant A. baumannii . Here, we show that a subpopulation of cells associated with the opaque/translucent colony phase variation by A. baumannii AB5075 displays differential tolerance to subinhibitory concentrations of colistin and tetracycline. Using a variety of microscopic techniques, we demonstrate that extracellular polysaccharide moieties mediate colistin tolerance to opaque A. baumannii at single-cell level and that mushroom-shaped biofilm structures protect opaque bacteria at the community level. The colony switch phenotype is found to alter several traits of A. baumannii , including long-term survival under desiccation, tolerance to ethanol, competition with Escherichia coli , and intracellular survival in the environmental model host Acanthamoeba castellanii . Additionally, our findings suggest that extracellular DNA associated with membrane vesicles can promote colony switching in a DNA recombinase-dependent manner. IMPORTANCE As a WHO top-priority drug-resistant microbe, Acinetobacter baumannii significantly contributes to hospital-associated infections worldwide. One particularly intriguing aspect is its ability to reversibly switch its colony morphotype on agar plates, which has been remarkably underexplored. In this study, we employed various microscopic techniques and phenotypic assays to investigate the colony phase variation switch under different clinically and environmentally relevant conditions. Our findings reveal that the presence of a poly N-acetylglucosamine-positive extracellular matrix layer contributes to the protection of bacteria from the bactericidal effects of colistin. Furthermore, we provide intriguing insights into the multicellular lifestyle of A. baumannii , specifically in the context of colony switch variation within its predatory host, Acanthamoeba castellanii .

show abstract

Section: Discussionmentioning

confidence: 99%

“…There are 11 structurally related TTTRs identified in the genome of A. baumannii . To inhibit TTTRs associated colony switch drive, the deletion of at least four of these genes is required ( 6 ).…”

Section: Introductionmentioning

confidence: 99%

Colony phase variation switch modulates antimicrobial tolerance and biofilm formation in Acinetobacter baumannii

Mushtaq,

Nadeem,

Yabrag

et al. 2024

Microbiol Spectr

View full text Add to dashboard Cite

show abstract

“…A phenotypic switch has been described in A. baumannii that generates virulent and avirulent subpopulations ( 40 – 42 ). Each cell variant can be distinguished by its colony morphology on agar plates using oblique lighting, with virulent variants forming opaque colonies (VIR-O) and avirulent variants forming translucent colonies (AV-T) ( 41 , 43 ). In addition to differences in virulence, the VIR-O variant possesses a thicker capsule than the AV-T variant; it is considerably more motile and secretes greater amounts of the quorum-sensing signal 3-hydroxy-dodecanoyl-l-homoserine lactone (3-OH-C 12 -HSL)( 40 , 43 ).…”

Section: Introductionmentioning

confidence: 99%

“…We recently demonstrated that the stochastic activation of a family of TetR-type transcriptional regulators (TTTRs) is able to drive the cells from the VIR-O state to many of the phenotypes associated with the AV-T state ( 43 ). Activation of the TTTR ABUW_1645 ( ABUW_RS08030 ) constitutes the preferred pathway to switch and it gives rise to avirulent AV-T variants.…”

Section: Introductionmentioning

confidence: 99%

Evidence for Rho-dependent control of a virulence switch in Acinetobacter baumannii

Pérez-Varela,

Singh,

Colquhoun

et al. 2024

mBio

Self Cite

View full text Add to dashboard Cite

Acinetobacter baumannii strain AB5075 is able to interconvert at high frequency between virulent cells that form opaque colonies (VIR-O) and avirulent cells that form translucent colonies (AV-T). Cells switch from the VIR-O to the AV-T state by the combinatorial activation of at least three TetR-type transcriptional regulators (TTTRs). A genetic screen identified the transcription termination factor Rho as a major contributor that controls expression differences of these TTTRs between VIR-O and AV-T cells. Each TTTR has a long mRNA leader region where transcripts are terminated in VIR-O cells. However, in AV-T cells, the degree of termination in each TTTR leader was greatly reduced, allowing for higher levels of TTTR expression. In a strain with decreased Rho expression, or in wild-type VIR-O cells treated with the Rho inhibitor bicyclomycin, the degree of termination in each TTTR mRNA leader region was reduced. Mutations in the leader region of one TTTR, ABUW_1645 , were identified that reduced the degree of termination. Purified Rho protein bound the leader region of the most frequently activated TTTR ABUW_1645 and the least frequently activated TTTR ABUW_1959 with similar affinities. This together with the observation that the levels of Rho protein were unchanged between VIR-O and AV-T cells, suggested that additional factors differentially modulate Rho activity between each variant. Finally, we demonstrate in AV-T cells that nutrient depletion is a condition that increases the levels of Rho-dependent transcription termination in the TTTR leader regions to regulate this phenotypic switch. IMPORTANCE Acinetobacter baumannii is a significant cause of infections in the healthcare setting. More recently, A. baumannii has been a leading cause of secondary bacterial pneumonia in patients infected with SARS-CoV-2 and the overall frequency of A. baumannii infection increased 78% during the COVID-19 pandemic. A. baumannii can exist in virulent or avirulent subpopulations and this interconversion is mediated by the expression of a family of TetR-type transcriptional regulators. In this study, we demonstrate that Rho is a key regulatory component in the expression of these TetR regulators. Overall, this study is the first to address a role for Rho in A. baumannii and provides additional evidence for the role of Rho in regulating diversity in bacterial subpopulations.

show abstract

“…Only seven A. baumannii ATCC17978 sRNAs are conserved (between 70-75% sequence identity) across selected members of the Pseudomonadales (e.g., Pseudomonas aeruginosa and Moraxella catarrhalis ) and none shares any sequence conservation with sRNAs in Enterobactericeae (Kröger et al ., 2018). A few sRNAs in A. baumannii have been functionally characterised and were shown to be involved in the regulation of efflux pumps, biofilm formation and phenotypic switching between virulent and avirulent phase variants (Sharma et al ., 2014; Álvarez-Fraga et al ., 2017; Anderson et al ., 2020; Pérez-Varela et al ., 2022; Shenkutie et al ., 2023). However, their direct targets and mechanism of action have not been dissected.…”

Section: Introductionmentioning

confidence: 99%

Global analysis of the RNA-RNA interactome inAcinetobacter baumanniiAB5075 uncovers a small regulatory RNA repressing the virulence-related outer membrane protein CarO

Hamrock,

Ryan,

Shaibah

et al. 2023

Preprint

View full text Add to dashboard Cite

Acinetobacter baumanniiis an opportunistic Gram-negative pathogen that infects critically ill patients. The emergence of antimicrobial resistantA. baumanniihas exacerbated the need to functionally characterise environmental adaptation, antibiotic resistance and pathogenicity of this organism and their genetic regulators to inform intervention strategies. Critical to rapid adaptation to changing environments in bacteria are small regulatory RNAs (sRNAs), however, the role that sRNAs play in the biology ofA. baumanniiis poorly understood. To assess the regulatory function of sRNAs and to uncover their RNA interaction partners inA. baumannii, we employed an RNA proximity ligation and sequencing method (Hi-GRIL-seq) in three different environmental conditions. We found that 40 sRNA candidates were ligated to sRNA-RNA chimeric sequencing reads, suggesting that sRNA-mediated gene regulation is pervasive inA. baumanniiand that sRNAs act as direct regulators of mRNA molecules through antisense base-pairing. In-depth characterisation uncovered the sRNA Aar to be a post-transcriptional regulator of four mRNA targets including that of the outer membrane protein CarO and the siderophore receptor BfnH. We show that Aar initiates base-pairing with these mRNA molecules using a conserved seed region of nine nucleotides, sequestering the ribosome binding sites and inhibiting translation. Aar is differentially expressed in response to multiple stress stimuli suggesting a role in fine-tuning translation of the Aar-target molecules inA. baumanniiunder hostile conditions. Together, our study provides mechanistic insights into sRNA-mediated gene expression control inA. baumanniiand represents a valuable resource for future RNA-centric research endeavours in this ESKAPE pathogen.

show abstract

Stochastic activation of a family of TetR type transcriptional regulators controls phenotypic heterogeneity in Acinetobacter baumannii

Cited by 9 publications

References 34 publications

Colony phase variation switch modulates antimicrobial tolerance and biofilm formation in Acinetobacter baumannii

Colony phase variation switch modulates antimicrobial tolerance and biofilm formation in Acinetobacter baumannii

Evidence for Rho-dependent control of a virulence switch in Acinetobacter baumannii

Global analysis of the RNA-RNA interactome inAcinetobacter baumanniiAB5075 uncovers a small regulatory RNA repressing the virulence-related outer membrane protein CarO

Contact Info

Product

Resources

About