title: Pili contribute to biofilm formation in vitro in Mycobacterium tuberculosis.
abstract: Organized bacterial communities, or biofilms, provide an important reservoir for persistent cells that are inaccessible or tolerant to antibiotics. Curli pili are cell-surface structures produced by certain bacteria and have been implicated in biofilm formation in these species. In order to determine whether these structures, which were suggested to be encoded by the Rv3312A (mtp) gene, have a similar role in Mycobacterium tuberculosis, we generated a Δmtp mutant and a mtp-complemented strain of a clinical isolate of M. tuberculosis and analyzed these strains for their ability to produce pili in comparison to the wild-type strain. Phenotypic analysis by transmission electron microscopy proved the essentiality of mtp for piliation in M. tuberculosis. We then compared biofilm formation of the derived strains in detergent-free Sauton's media. Biofilm mass was quantified spectrophotometrically using crystal violet. Furthermore, we examined mtp gene expression by quantitative real-time PCR in wild-type cells grown under biofilm versus planktonic growth conditions. We found a 68.4 % reduction in biofilm mass in the mutant compared to the wild-type strain (P = 0.002). Complementation of the mutant resulted in a restoration of the wild-type biofilm phenotype (P = 0.022). We, however, found no significant difference between mtp expression in cells of the biofilm to those growing planktonically. Our findings highlight a crucial, but non-specific, role of pili in the biofilm lifestyle of M. tuberculosis and indicate that they may represent an important target for the development of therapeutics to attenuate biofilm formation, thereby potentially reducing persistence.
authors.affiliation: Medical Microbiology and Infection Control, School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, 1st floor Doris Duke Medical Research Institute, Congella, Private Bag 7, Durban, 4013, South Africa.
authors.forename: Saiyur
authors.initials: S
authors.lastname: Ramsugit
authors.forename: Sinenhlanhla
authors.initials: S
authors.lastname: Guma
authors.forename: Balakrishna
authors.initials: B
authors.lastname: Pillay
authors.forename: Paras
authors.initials: P
authors.lastname: Jain
authors.forename: Michelle H
authors.initials: MH
authors.lastname: Larsen
authors.forename: Siva
authors.initials: S
authors.lastname: Danaviah
authors.forename: Manormoney
authors.initials: M
authors.lastname: Pillay
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms / Q000254:growth & development*; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D017353:Gene Deletion; D020869:Gene Expression Profiling; D005816:Genetic Complementation Test; D005840:Gentian Violet / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D060888:Real-Time Polymerase Chain Reaction; D013194:Staining and Labeling
chemical_list: D001426:Bacterial Proteins; D005840:Gentian Violet