Studying the role of the AdeIJK RND efflux pump and its transcriptional regulator AdeN in the resistance and virulence of Acinetobacter baumannii
| dc.contributor.author | Unger, Mark | |
| dc.contributor.examiningcommittee | Oresnik, Ivan (Microbiology) Zhanel, George (Medical Microbiology) | en_US |
| dc.contributor.supervisor | Kumar, Ayush (Microbiology) | en_US |
| dc.date.accessioned | 2017-09-07T20:24:22Z | |
| dc.date.available | 2017-09-07T20:24:22Z | |
| dc.date.issued | 2017 | |
| dc.degree.discipline | Microbiology | en_US |
| dc.degree.level | Master of Science (M.Sc.) | en_US |
| dc.description.abstract | Acinetobacter baumannii, a Gram-negative bacterium, is a problematic opportunistic pathogen due to its resistance to multiple antibiotics. Energy-dependent efflux of antibiotics mediated by proteins belonging to the Resistance-Nodulation-Division (RND) family is the predominant mechanism of intrinsic resistance in A. baumannii. AdeIJK is one such pump that is known to efflux a multitude to antibiotics in A. baumannii. AdeN, a TetR-family protein, has been previously shown to act as a repressor of the AdeIJK efflux pump. However, unlike other RND efflux pump regulators in A. baumannii adeN is not a linked to the adeIJK operon, it is instead located 813kbp upstream of the adeIJK efflux pump-encoding operon. Previous study by our group of the triclosan-resistant mutant AB042, which has a 73bp deletion in adeN, showed changes in the expression of a significant number of genes and proteins, indicating that AdeN may be acting as a global transcription regulator in A. baumannii. To study the role of AdeN, we have created an unmarked deletion mutant of adeN (AB141) in ATCC17978. Quantitative reverse transcriptase PCR in combination with transcriptomic and proteomic analysis was performed on AB141 to determine if AdeN is acting as a global transcription regulator. Biofilm formation, motility, virulence, antibiotic susceptibility, and microbial growth were also evaluated to assess the phenotypic effect of adeN deletion on A. baumannii. Transcriptomic and proteomic analysis of AB141 showed that adeN deletion results in differential expression of 106 genes greater than 1.5log(2) fold. Using a proteomics approach, we detected 31 proteins whose expression was altered greater than 1.5 fold. Phenotypic testing led to the observation that deletion of adeN results in decreased susceptibility to antibiotics and osmotic stress. The adeN deletion mutant also exhibited attenuated virulence, decreased biofilm formation and motility. In order to determine if the observed phenotypes were a result of overexpression of AdeIJK rather than loss of AdeN expression, an adeIJK deletion mutant (AB185) and a double mutant of adeN 7 and adeIJK (AB186) were created in ATCC17978 background and phenotypically evaluated alongside the adeN mutant AB141. Intriguingly both adeIJK deletion mutants also exhibited attenuated virulence and motility compared to wild-type. These data indicate that AdeN likely plays a much larger role as a global regulator in A. baumannii with respect to resistance and virulence, however the interactions between AdeN and AdeIJK are much more complicated than originally thought. | en_US |
| dc.description.note | October 2017 | en_US |
| dc.identifier.uri | http://hdl.handle.net/1993/32505 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | Transcription Regulation | en_US |
| dc.title | Studying the role of the AdeIJK RND efflux pump and its transcriptional regulator AdeN in the resistance and virulence of Acinetobacter baumannii | en_US |
| dc.type | master thesis | en_US |