During active growth of Escherichia coli, majority of the transcriptional activity is carried out by the housekeeping sigma factor (σ70), whose assoc

Antibiotic resistance is one of the most serious challenges that the world is currently facing. The number of people succumbing to drug-resistant infections is increasing every day, but the rate of drug discovery has failed to match the requisite demands. Most of the currently known antibiotics target the three essential pathways of central dogma. However, bacteria have evolved multiple mechanisms to survive these antibiotics. Consequently, there is an urgent necessity to target auxiliary pathways for the discovery of new drugs. Metabolism-related and stress-associated pathways are ideal in this regard. The stringent response pathway regulated by the signaling nucleotides (p)ppGpp is an attractive target as inhibition of the pathway would in turn decrease the persistence and long-term survival of pathogenic bacteria. In this perspective, we focus on the recent design of small molecule analogues of (p)ppGpp that have yielded promising results in terms of growth and biofilm inhibition. Additionally, we discuss how targeting small RNAs and riboswitches, as well as antimicrobial peptides, would help combat drug-resistant infections in the near future.

Antibiotic resistance is a massive and serious threat to human welfare and healthcare. Apart from being genetically resistant to antibiotics, the other important mechanism by which bacteria can evade antibiotics is multidrug tolerance. Here cells enter into a transiently nongrowing phase, and as a result, latent infection remains inside the host, causing disease recurrence. Biofilm-derived antibiotic tolerance and persister formation of the pathogenic bacteria inside the host remain a serious issue of treatment failure and recurrent chronic infection in the case of all major pathogens. As a result, new chemotherapeutic agents are sought that specifically inhibit biofilm formation or maturation as well as cause the dispersion of mature biofilms, thus allowing the conventional drugs to kill sensitive cells residing inside. This mini-review attempts to analyze different small-molecule-based chemical approaches that have been used to enable bacterial biofilm inhibition at different steps of maturation.

The bacterial second messenger cyclic diguanosine monophosphate (c-di-GMP) plays an important role in a variety of cellular functions, including biofilm formation, alterations in the cell surface, host colonization and regulation of bacterial flagellar motility, which enable bacteria to survive changing environmental conditions. The cellular level of c-di-GMP is regulated by a balance between opposing activities of diguanylate cyclases (DGCs) and cognate phosphodiesterases (PDE-As). Here, we report the presence and importance of a protein, MSDGC-1 (an orthologue of Rv1354c in Mycobacterium tuberculosis), involved in c-di-GMP turnover in Mycobacterium smegmatis. MSDGC-1 is a multidomain protein, having GAF, GGDEF and EAL domains arranged in tandem, and exhibits both c-di-GMP synthesis and degradation activities. Most other proteins containing GGDEF and EAL domains have been demonstrated to have either DGC or PDE-A activity. Unlike other bacteria, which harbour several copies of the protein involved in c-di-GMP turnover, M. smegmatis has a single genomic copy, deletion of which severely affects long-term survival under conditions of nutrient starvation. Overexpression of MSDGC-1 alters the colony morphology and growth profile of M. smegmatis. In order to gain insights into the regulation of the c-di-GMP level, we cloned individual domains and tested their activities. We observed a loss of activity in the separated domains, indicating the importance of full-length MSDGC-1 for controlling bifunctionality.