Insecticidal Pilin Subunit from the Insect Pathogen Xenorhabdus nematophila

Xenorhabdus nematophila is an insect pathogen and produces protein toxins which kill the larval host. Previously, we characterized an orally toxic, large, outer membrane-associated protein complex from the culture medium of X. nematophila. Here, we describe the cloning, expression, and characterization of a 17-kDa pilin subunit of X. nematophila isolated from that protein complex. The gene was amplified by PCR, cloned, and expressed in Escherichia coli. The recombinant protein was refolded in vitro in the absence of its cognate chaperone by using a urea gradient. The protein oligomerized during in vitro refolding, forming multimers. Point mutations in the conserved N-terminal residues of the pilin protein greatly destabilized its oligomeric organization, demonstrating the importance of the N terminus in refolding and oligomerization of the pilin subunit by donor strand complementation. The recombinant protein was cytotoxic to cultured Helicoverpa armigera larval hemocytes, causing agglutination and subsequent release of the cytoplasmic enzyme lactate dehydrogenase. The agglutination of larval cells by the 17-kDa protein was inhibited by several sugar derivatives. The biological activity of the purified recombinant protein indicated that it has a conformation similar to that of the native protein. The 17-kDa pilin subunit was found to be orally toxic to fourth- or fifth-instar larvae of an important crop pest, H. armigera, causing extensive damage to the midgut epithelial membrane. To our knowledge, this is first report describing an insecticidal pilin subunit of a bacterium

The Effect of COVID-19 on Gut Microbiota: Exploring the Complex Interplay and Implications for Human Health

The COVID-19 pandemic caused by the SARS-CoV-2 virus has led to significant global health implications. Although the respiratory manifestations of COVID-19 are widely recognized, emerging evidence suggests that the disease may also significantly affect the gut microbiota, the intricate community of bacteria that lives within the gastrointestinal system. This extensive article intends to investigate the impact of COVID-19 on the gut microbiota, examining the underlying mechanisms, clinical implications, and potential therapeutic interventions. Understanding the complex interactions between COVID-19 and the gut microbiota will help us to gain valuable insights into the broader consequences of this viral infection on human health