Characterization of permissive and non-permissive peptide insertion sites in chloramphenicol acetyltransferase

The Structural Permissiveness of Triosephosphate Isomerase (TpiA) of Escherichia coli

Triosephosphate isomerase (TpiA) is widely regarded as an example of an optimally evolved enzyme due to its essential role in biological systems, its structural conservation, and its near-perfect kinetic parameters. In this study, we investigated the structural robustness of the archetypal TpiA variant from Escherichia coli using an in vitro 5-amino acid linker scanning method. The resulting library was introduced into a tpiA mutant strain for functional complementation. From this library, 16 TpiA variants that were phenotypically indistinguishable from the wild-type enzyme were selected for further analysis. Although all variants retained enzymatic activities within the wild-type range, several insertions were found in highly structured protein domains where the linker was expected to cause significant structural perturbations. Despite these potentially disruptive additions, the enzymes maintained their activity even when expressed in a dnaK mutant, suggesting that chaperones did not compensate for structural abnormalities in vivo. Additionally, when these mutant TpiA variants were produced using an in vitro transcription/translation system, they exhibited enzymatic activity comparable to, and in some cases exceeding, that of the non-mutated enzyme. AlphaFold2 exposed that insertions reconstructed the local architecture of the nearby amino acid sequences. The evolutionary implications of this remarkable structural resilience are discussed.

Antibiotic-Resistant Salmonella in Animal Products Jeopardize Human Health

Despite the significance of antibiotics in treating bacterial infections, antibiotic resistance is continuously increasing, thus posing a significant threat. In addition to strains resistant to individual drugs, multidrug-resistant (MDR) and pandrug-resistant strains, are emerging. Salmonella, a primary cause of global foodborne illness, is often transmitted through animal products. Antibiotic treatment is crucial for immunocompromised individuals, such as older adults and patients with weakened immune systems, due to their increased susceptibility to severe effects. MDR Salmonella, which can arise following antibiotic use in food animals, may transfer to humans, leading to significant health challenges. The emergence of Salmonella strains resistant to carbapenems, often considered a last-resort antibiotic class, is particularly concerning. Salmonella neutralizes antibiotics through mechanisms, such as horizontal gene transfer via plasmids, efflux/influx system regulation, and enzyme production that deactivate or alter antibiotics. The rise of megaplasmids in Salmonella is particularly alarming, as it may enable resistance to a broader range of antibiotics. This review summarizes the current state of the growing threat of MDR Salmonella and underscores the urgent need for a coordinated response.

Environmental antibiotics and resistance genes as emerging contaminants: Methods of detection and bioremediation

In developing countries, the use of antibiotics has helped to reduce the mortality rate by minimizing the deaths caused by pathogenic infections, but the costs of antibiotic contamination remain a major concern. Antibiotics are released into the environment, creating a complicated environmental problem. Antibiotics are used in human, livestock and agriculture, contributing to its escalation in the environment. Environmental antibiotics pose a range of risks and have significant effects on human and animal health. Nevertheless, this is the result of the development of antibiotic-resistant and multi-drug-resistant bacteria. In the area of health care, animal husbandry and crop processing, the imprudent use of antibiotic drugs produces antibiotic-resistant bacteria. This threat is the deepest in the developing world, with an estimated 700,000 people suffering from antibiotic-resistant infections each year. The study explores how bacteria use a wide variety of antibiotic resistance mechanism and how these approaches have an impact on the environment and on our health. The paper focuses on the processes by which antibiotics degrade, the health effects of these emerging contaminants, and the tolerance of bacteria to antibiotics.