Cell wall metabolism in Bacillus subtilis

PhD ThesisCell wall is a unique and essential component of bacterial cell. It defines cell shape and protects cell from bursting through its own internal osmotic pressure. It also represents a significant drain on the cells resources, particularly in Gram positives, where the wall accounts for more than 20 % of the dry weight of the cell, and approximately 50 % of ‘‘old’’ cell wall is degraded and new material made to permit cell growth. After the discovery of penicillin, there has been active study of bacterial cell wall structure and metabolism, as it represents the major target for antibacterial compounds. The biosynthetic pathways for cell wall precursors has been well investigated in bacteria generally, but the coordination of cell wall metabolic processes and the fate of turnover cell wall materials have only been well characterised in Gram-negative bacteria (e.g Escherichia coli). In Gram-positive bacteria, it has generally been accepted that the old wall is released from the surface and lost to the environment during growth, with apparent recycling of this material during stationary phase for Bacillus subtilis. It is also known that the Gram-positive wall is subject to significant post-synthetic processing, involving the linkage of wall teichoic acids and the cleavage of molecules from the structure, e.g. D-alanine, although the function of these is unclear. Understanding the importance of these processes has relevance for both the pathogenicity and biotechnological use of bacteria, as well as for understanding bacterial cell biology. As it is known that the peptidoglycan fragments (e.g muropeptides) induce the innate immune response in higher organisms and so act as a signal for infection, particularly for Gram-positive bacteria. Thus, understanding how they are generated and recycled by the bacteria may offer potential insights into novel therapeutics, also the accumulation of cell wall muropeptides should be avoided in biotechnological products. In this thesis, the D-alanine metabolism was manipulated to understand the mechanistic details of cell wall metabolism and D-alanine recycling in B. subtilis, using genetic, biochemical, bioinformatics and fluorescent microscopy approaches. Through these analyses, a D-alanine transporter (DatA, formerly YtnA) was identified by genetic screening. The roles of DatA and the carboxypeptidases, LdcB and DacA, in recycling of cell wall derived D-alanine have experimentally been confirmed. We also found that D-alanine aminotransferase (Dat) can act to synthesis D-alanine under certain conditions. From the data obtained a model for peptidoglycan assembly (coordinated synthesis and turnover) during growth of B. subtilis has been developed to take into account the various aspects of cell wall metabolism.Kurdistan regional government-IRA

Does Early Childhood Vaccination Protect Against COVID-19?

The coronavirus disease 2019 (COVID-19) is an on-going pandemic caused by the SARS-coronavirus-2 (SARS-CoV-2) which targets the respiratory system of humans. The published data show that children, unlike adults, are less susceptible to contracting the disease. This article aims at understanding why children constitute a minor group among hospitalized COVID-19 patients. Here, we hypothesize that the measles, mumps, and rubella (MMR) vaccine could provide a broad neutralizing antibody against numbers of diseases, including COVID-19. Our hypothesis is based on the 30 amino acid sequence homology between the SARS-CoV-2 Spike (S) glycoprotein (PDB: 6VSB) of both the measles virus fusion (F1) glycoprotein (PDB: 5YXW_B) and the rubella virus envelope (E1) glycoprotein (PDB: 4ADG_A). Computational analysis of the homologous region detected the sequence as antigenic epitopes in both measles and rubella. Therefore, we believe that humoral immunity, created through the MMR vaccination, provides children with advantageous protection against COVID-19 as well, however, an experimental analysis is required

Factors Contributing to the Containment of the COVID-19 in Kurdistan Region of Iraq

A highly contagious coronavirus disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which was first identified in Wuhan, China in December 2019. The virus primarily affects the respiratory system of human beings and results in the symptoms of headache, fever, dry cough, sore throat, shortness of breath and fatigue with abnormal chest computed tomography (CT) scan. In some cases, nasal sputum discharge and diarrhea have been also reported. Up to the 26th of April 2020, more than three million laboratory confirmed cases of COVID-19 have been recorded worldwide with more than 220,000 confirmed deaths. In the Kurdistan region of Iraq, the first case of laboratory confirmed COVID-19 was recorded in March 1st, 2020 in Sulaymaniyah province.&nbsp

Structure of the LdcB LD-carboxypeptidase reveals the molecular basis of peptidoglycan recognition

Peptidoglycan surrounds the bacterial cytoplasmic membrane to protect the cell against osmolysis. The biosynthesis of peptidoglycan, made of glycan strands crosslinked by short peptides, is the target of antibiotics like β-lactams and glycopeptides. Nascent peptidoglycan contains pentapeptides that are trimmed by carboxypeptidases to tetra- and tripeptides. The well-characterized DD-carboxypeptidases hydrolyze the terminal D-alanine from the stem pentapeptide to produce a tetrapeptide. However, few LD-carboxypeptidases that produce tripeptides have been identified, and nothing is known about substrate specificity in these enzymes. We report biochemical properties and crystal structures of the LD-carboxypeptidases LdcB from Streptococcus pneumoniae, Bacillus anthracis, and Bacillus subtilis. The enzymes are active against bacterial cell wall tetrapeptides and adopt a zinc-carboxypeptidase fold characteristic of the LAS superfamily. We have also solved the structure of S. pneumoniae LdcB with a product mimic, elucidating the residues essential for peptidoglycan recognition and the conformational changes that occur on ligand binding. © 2014 The Authors