Rv2223c, an acid inducible carboxyl-esterase of Mycobacterium tuberculosis enhanced the growth and survival of Mycobacterium smegmatis

Identification and Quantification of S-Sulfenylation Proteome of Mycobacterium tuberculosis under Oxidative Stress

The ability to maintain redox homeostasis is critical for Mycobacterium tuberculosis (Mtb) to survive the redox stress of the host. There are many antioxidant systems in Mtb to ensure its normal replication and survival in the host, and cysteine thiols are one of them. S-sulfenylation is one of the reversible modifications of cysteine thiols to resist oxidative stress. In the study, we investigated the total cysteine thiols modification and S-sulfenylation modification of Mtb proteome under the oxidative stress provided by hydrogen peroxide. To determine and quantify the S-sulfenylation modified proteins, high specific IodoTMT6plex reagents and high resolution mass spectrometry were used to label and quantify the peptides and proteins modified. There are significant differences for the total cysteine modification levels of 279 proteins and S-sulfenylation modification levels of 297 proteins under hydrogen peroxide stress. Functional enrichment analysis indicated that these cysteine-modified proteins were involved in the oxidation-reduction process, fatty acid biosynthetic process, stress response, protein repair, cell wall, etc. In conclusion, our study provides a view of cysteine modifications of the Mtb proteome under oxidative stress, revealing a series of proteins that may play a role in maintaining redox homeostasis. IMPORTANCE With the continuous spread of drug-resistant tuberculosis, there is an urgent need for new antituberculosis drugs with new mechanisms. The ability of Mtb to resist oxidative stress is extremely important for maintaining redox homeostasis and survival in the host. The reversible modifications of cysteine residues have a dual role of protection from irreversible damage to protein functions and regulation, which plays an important role in the redox homeostasis system. Thus, to discover cysteine modification changes in the proteome level under oxidative stress is quintessential to elucidate its antioxidant mechanism. Our results provided a list of proteins involved in the antioxidant process that potentially could be considered targets for drug discovery and vaccine development. Furthermore, it is the first study to determine and quantify the S-sulfenylation-modified proteins in Mtb, which provided better insight into the Mtb response to the host oxidative defense and enable a deeper understanding of Mtb survival strategies.

Correlation of over-expression of rv1900c with enhanced survival of M. smegmatis under stress conditions: Modulation of cell surface properties

Mycobacterium tuberculosis has distinct cell wall composition that helps in intracellular survival of bacteria. Rv1900c, a two domain protein, has been grouped in lip gene family. The expression of rv1900c was upregulated under acidic, nutritive and iron stress conditions in M. tuberculosis H37Ra. To investigate the biological effect of Rv1900c in mycobacterium physiology, rv1900c gene was cloned in M. smegmatis, a surrogate host. Its counterpart MSMEG_4477 in M. smegmatis demonstrated 38% protein similarity with Rv1900c. MSMEG_4477 gene was knocked out in M. smegmatis by homologous recombination. rv1900c and MSMEG_4477 genes, cloned in pVV16, were expressed in the M. smegmatis knockout strain (M. smegmatis ΔMSMEG_4477). Gene knockout significantly altered colony morphology and growth kinetics of M. smegmatis. M. smegmatis ΔMSMEG_1900 (pVV16::rv1900c) colonies were less wrinkled and had smooth surface as compared to M. smegmatis ΔMSMEG_4477. The changes were reverted back to normal upon expression of MSMEG_4477 in knockout strain M. smegmatis ΔMSMEG_4477 (pVV16::MSMEG_4477). The expression of rv1900c enhanced the biofilm formation and survival of bacteria under various in vitro stresses like acidic, nutritive stress, including lysozyme, SDS and multiple antibiotics treatment in comparison to control. On the other hand the expression of rv1900c decreased the cell wall permeability. The resistance provided by M. smegmatis ΔMSMEG_4477 (pVV16::MSMEG_4477) was comparable to M. smegmatis having vector alone (MS_vec). The lipid content of M. smegmatis ΔMSMEG_1900 (pVV16::rv1900c) was observed to be different from M. smegmatis ΔMSMEG_4477 (pVV16::MSMEG_4477). M. smegmatis ΔMSMEG_1900 (pVV16::rv1900c) was more tolerant to stress conditions in comparison to M. smegmatis ΔMSMEG_4477 (pVV16::MSMEG_4477). Expression of rv1900c enhanced the intracellular survival of mycobacteria. Therefore, the present study suggested an association of Rv1900c to the stress tolerance by cell wall modification that might have resulted in enhanced intracellular survival of the mycobacteria.

High-Throughput Screen for Cell Wall Synthesis Network Module in Mycobacterium tuberculosis Based on Integrated Bioinformatics Strategy

BACKGROUND

Mycobacterium tuberculosis is one of the deadliest pathogens in humans. Co-infection of M. tuberculosis with HIV and the emergence of multi-drug-resistant tuberculosis (TB) constitute a serious global threat. However, no effective anti-TB drugs are available, with the exception of first-line drugs such as isoniazid. The cell wall of M. tuberculosis, which is primarily responsible for the lack of effective anti-TB drugs and the escape of the bacteria from host immunity, is an important drug target. The core components of the cell wall of M. tuberculosis are peptidoglycan, arabinogalactan, and mycotic acid. However, the functional genome and metabolic regulation pathways for the M. tuberculosis cell wall are still unknown. In this study, we used the biclustering algorithm integrated into cMonkey, sequence alignment, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and other bioinformatics methods to scan the whole genome of M. tuberculosis as well as to identify and statistically analyze the genes related to the synthesis of the M. tuberculosis cell wall.

METHOD

We performed high-throughput genome-wide screening for M. tuberculosis using Biocarta, KEGG, National Cancer Institute Pathway Interaction Database (NCI-PID), HumanCyc, and Reactome. We then used the Database of Origin and Registration (DOOR) established in our laboratory to classify the collection of operons for M. tuberculosis cell wall synthetic genes. We used the cMonkey double clustering algorithm to perform clustering analysis on the gene expression profile of M. tuberculosis for cell wall synthesis. Finally, we visualized the results using Cytoscape.

RESULT AND CONCLUSION

Through bioinformatics and statistical analyses, we identified 893 M. tuberculosis H37Rv cell wall synthesis genes, distributed in 20 pathways, involved in 46 different functions related to cell wall synthesis, and clustered in 386 modules. We identified important pivotal genes and proteins in the cell wall synthesis pathway such as murA, a class of operons containing genes involved in cell wall synthesis such as ID6951, and a class of operons indispensable for the survival of the bacteria. In addition, we found 41 co-regulatory modules for cell wall synthesis and five co-expression networks of molecular complexes involved in peptidoglycan biosynthesis, membrane transporter synthesis, and other cell wall processes.