MSP2 strain showed low expression of glnA1 gene as compared to the expression in other strains in low nitrogen condition because there was no regulation at transcriptional level due to lack of P1 promoter

hence lack of GlnR binding motif also. PLG layer has been known to be present in the cell wall of only virulent strains Vismodegib of mycobacteria [16, 23]. Harth and colleagues indicated that extracellular GS of pathogenic mycobacteria is involved in synthesis of this layer [10, 24, 25]. There has also been reports stating the involvement of PLG layer of M. bovis in cell wall strength and in providing resistance to various physical and chemical stress factors [8]. The absence of PLG layer from the cell wall of mycobacteria grown in high see more nitrogen condition indirectly suggest that PLG layer may be a form of nitrogen assimilation in pathogenic mycobacteria. In macrophages, mycobacteria encounter nitrogen stress which leads to high GS expression and PLG layer synthesis

in the cell wall. Immunogold localization and PLG isolation studies further validated the finding of no detectable PLG in the cell wall of M. bovis, MSFP, MSP1 and MSP2 strains when grown in high nitrogen conditions. The ability of the pathogenic mycobacteria to form biofilm adds on to their Torin 1 molecular weight virulence potential [26]. Biofilm formed at air liquid interface are popularly known as pellicle. Additionally, mycolic acids are the major component of the biofilms formed by mycobacterial species [26, 27] but it is not clearly known whether mycolic acid synthesis or its amount in cell wall is affected by PLG layer. However, there are few reports that suggest the involvement of PLG layer in biofilm formation [8]. A ∆glnA1 strain of M. bovis that

lack PLG layer in the cell wall was found to be defective in biofilm formation [8]. Additionally, our results showed that the biofilm and pellicle forming capability STK38 of M. smegmatis strain complemented with M. bovis glnA1 was enhanced than the wild type. This is due to the fact that higher expression of M. bovis glnA1 leads to the synthesis of PLG layer in the M. smegmatis complemented with M. bovis glnA1[8]. There are reports also suggesting that microbial amyloids play a significant role in biofilms of actinobacteria [28, 29]. Additionally, it was observed that biofilm was formed significantly much better in low nitrogen conditions which added to the involvement of PLG layer in biofilm formation. There is a gap in our understanding of the exact mechanisms and enzymes involved in the synthesis of PLG layer till date. In addition to it, characterization of PLG layer, can further help in our understanding of complex mycobacterial cell wall. Because of high molecular weight and inert nature of the polymer it may also act as an adjuvant. This needs further investigation.