Biology subjects

Sharifian Gh., M.

Publications and source records attributed to Sharifian Gh., M..

3 recordsLinked to original sources

bioRxiv2024

Targeting Iron - Respiratory Reciprocity Promotes Bacterial Death

Discovering new bacterial signaling pathways offers unique antibiotic strategies. Here, through an unbiased resistance screen of 3,884 gene knockout strains, we uncovered a previously unknown non-lytic bactericidal mechanism that sequentially couples three transporters and downstream transcription to lethally suppress respiration of the highly virulent P. aeruginosa strain PA14 - one of three species on the WHOs Priority 1: Critical list. By targeting outer membrane YaiW, cationic lacritin peptide N-104 translocates into the periplasm where it ligates outer loops 4 and 2 of the inner membrane transporters FeoB and PotH, respectively, to suppress both ferrous iron and polyamine uptake. This broadly shuts down transcription of many biofilm-associated genes, including ferrous iron-dependent TauD and ExbB1. The mechanism is innate to the surface of the eye and is enhanced by synergistic coupling with thrombin peptide GKY20. This is the first example of an inhibitor of multiple bacterial transporters.

microbiology↗

bioRxiv2023

Bioluminescence-Based Determination of Cytosolic Accumulation of Antibiotics in Escherichia coli

Antibiotic resistance is an alarming public health concern that affects millions of individuals across the globe each year. A major challenge in the development of effective antibiotics lies in their limited ability to permeate into cells, noting that numerous susceptible antibiotic targets reside within the bacterial cytosol. Consequently, improving cellular permeability is often a key consideration during antibiotic development, underscoring the need for reliable methods to assess the permeability of molecules across cellular membranes. Currently, methods used to measure permeability often fail to discriminate between arrival within the cytoplasm and the overall association of molecules with the cell. Additionally, these techniques typically possess throughput limitations. In this work, we describe a luciferase-based assay designed for assessing the permeability of molecules into the cytosolic compartment of Gram-negative bacteria. Our findings demonstrate a robust system that can elucidate the kinetics of intracellular antibiotics accumulation in live bacterial cells in real time.

microbiology↗

bioRxiv2020

Determination of Bacterial Surface Charge Density Via Saturation of Adsorbed Ions

Bacterial surface charge is a critical characteristic of the cells interfacial physiology that influences how the cell interacts with the local environment. A direct, sensitive, and accurate experimental technique capable of quantifying bacterial surface charge is needed to better understand molecular adaptations in interfacial physiology in response to environmental changes. We introduce here the method of second harmonic light scattering (SHS) which is capable of detecting the number of molecular ions adsorbed as counter charges on the exterior bacterial surface, thereby providing a measure of the surface charge. In this first demonstration, we detect the small molecular cation, malachite green, electrostatically adsorbed on the surface of representative strains of Gram-positive and Gram-negative bacteria. Surprisingly, the SHS deduced molecular transport rates through the different cellular ultra-structures are revealed to be nearly identical. However, the adsorption saturation densities on the exterior surfaces of the two bacteria were shown to be characteristically distinct. The negative charge density of the lipopolysaccharide coated outer surface of Gram-negative E. coli (8.7{+/-}1.7 nm-2) was deduced to be seven times larger than that of the protein surface layer of Gram-positive L. rhamnosus (1.2{+/-}0.2 nm-2). The feasibility of SHS deduced bacterial surface charge density for Gram-type differentiation is presented. STATEMENT of SIGNIFICANCEBacterial surface charge density is an important physiological characteristic which determines how the cell interacts with its local environment. Directly measuring the surface charge density, however, is experimentally non-trivial. In this work, we report an experimental method, second harmonic light scattering, that can directly and accurately quantify the surface charge density of individual living bacteria. This is achieved by measuring the number of molecular ions electrostatically adsorbed on the exterior cellular surface as counter charges. It is found that the negative charge density of a representative Gram-negative bacterium is 7 times larger than a representative Gram-positive bacterium. It is suggested that this disparity of surface charge density can be exploited as a basis for Gram-classification of bacteria.

biophysics↗