What Is Type VI Secretion System?

Strains of Escherichia coli and Citrobacter rodentium contain set of operons called the locus enterocyte effacement (LEE) region in their genomes. This region encodes a type III secretion system (T3SS).

SPI-3 contains only four ORFs encoding proteins with a known function have been studied. This island encodes proteins with no clear functional relationship to each other, which were involved in initial attachment and long-term persistence and survival during systemic dissemination (5, 6).

Toxic shock syndrome toxin-1 (TSST-1) is a protein encoded by tstH gene (H refers to human isolate) present on the bacterial chromosome within a mobile genetic element called staphylococcal pathogenicity island 1. TSST-1 is translated as a precursor protein with 234 amino acids and secreted after cleavage of 40 amino acids signal sequence located at its amino terminus. The mature protein of TSST-1 is a 22-30 kDa single- chain polypeptide including 194 amino acid residues (Cathleen A.E. et al., 1998; Debra L.M. et al., 1996). The 3D structures of TSST-1 and various mutants are known as they have been crystallized and analyzed by X-ray diffraction. TSST-1 is composed of two domains. Domain A consists of N-terminal α-helix (α-1) (residues 1-17) surrounded by five β-strands (residues 18-89).

Virulence-associated proteins (Vaps) are a particular class of type-II TA systems characterized by a bi-cistronic locus encoding a proteolytically labile antitoxin (VapB), typically followed by a stable toxin (VapC). These proteins were first identified in connection with virulence plasmids in human pathogens, such as Salmonella Dublin (7), but have since been recognized as one of the most predominant forms of type-II toxins, particularly among the archaea (8). A central component of VapC toxin activity is a PIN-domain, occurring within the approximately 100-amino acid sequence, that displays divalent cation-dependent ribonucleolytic

Did you even know that antimicrobial peptides kills bacteria. Then when you do that the holes break down the bacteria cell’s ability to function. It can also attack protozoa. Even fungi and viruses can be attacked too. But it can be attacked in different ways.

Over two decades ago, researches at Umea University in Sweden made an astounding discovery. They found out that bacteria can multiply disease-inducing genes that are essential to spread the infection quickly, focusing on a particular bacteria called Yersinia and on its structure called T3SS that allows it to transfer bacterial proteins into the host cell and destroy its metabolism. The T3SS is made up by more than 20 proteins that are membrane embedded. When the infection process starts, the bacteria receive an external signal from the host environment and begin to assemble the constituents of the secretion system. The characteristic of T3SS is the needle also called injectisome. The Bacterial proteins pass from the bacterial cytoplasm through the needle into the host cytoplasm, there are three membranes between the two cytoplasms .The needle provides a smooth passage through membranes, it starts at the cytoplasm of the bacterium pass through the two membranes and projects from the cell,

Study of inhibiting the type III secretion system (T3SS) is important because T3SS helps gram-negative bacteria sense other eukaryotic organism and secrets proteins that help the bacteria infect other organisms. T3SS activity is often seen as a requirement for many pathogenic bacteria to infect their hosts cells – such bacteria include E. coli, Salmonella, Yersinia, and Chlamydia. Much like in the first paper, the researchers’s analysis of the biosynthetic pathway helped them identify the gene cluster that led to the production of the T3SS, giving more insight into how the mechanism worked and how to suppress

Bacterial cells eukaryotes have a cell wall that provides protection to the bacterial cells. Targeting of the cell wall would result in interruption of bacterial cell structure which would result in an osmotic imbalance resulting into cell

Dr. Zemer Gitai received his bachelor’s degree from the MIT, and after this he completed his graduate endeavors from the UCSF. During this time, he concentrated in working on axon guidance in Caeorhabditis elegalns because he wanted to find out where the worm’s neurons came from and how they worked. This was the start of his interest in how small molecules such as proteins worked together as a complex system, and how spatial cues were being controlled. Dr. Gitai later joined Princeton University’s faculty and became the Director of Graduate Studies for the Department of Molecular Biology. Now Dr. Gitai focuses on the cell biology of bacteria and how their cells are able to self-organize across spatial scales.

To infect a host cell, the bacteriophage secures itself to the bacteria’s cell wall, precisely on a receptor found on the bacteria’s surface. When it becomes firmly bounded to the cell, the bacterial virus injects its genetic material (its nucleic acid) into the host cell. Relying on the form or group of phage, one of two cycles will occur; the lytic or lysogenic cycle. During a lytic cycle, the phage will make use of the host cell’s chemical energy along with its biosynthetic machinery in order to produce phage nucleic acids (phage DNA and phage mRNA) and phage proteins. Once the construction phase is complete, the phage nucleic acids and structural proteins are then brought together. After a while, certain proteins created within the cell

Virulence Factors: The most important virulence factor of S. aureus is the specific surface proteins that allow the organism to attach to host proteins. The surface proteins of this bacterium allow it to attach to host proteins such as laminin and fibronectin, which form the extracellular matrix of epithelial and endothelial cells. S. aureus also produces a number of membrane damaging toxins that allow the organism to further invade and harm the host, of which the alpha- toxin is the most well studied and is the protein responsible for septic shock. The alpha- toxin is a protein that binds to a specific receptor in platelets and monocytes in humans, forming pores that eventually destroy the cell.

abortus (as well as other bacteria such as E. coli and S. typhimurium) possess HF-1 an RNA-binding protein that regulates a set of genes which are essential for survival in the stationary phase of their life cycle [2, 3]. A mutation in the hfq gene (which codes for HF-1) of Brucella was shown to result in defective stationary-phase physiology [3]; this mutant was susceptible to acidic pH and free radicals, and also lost its viability more quickly than the wild-type strain. Differential gene expression of the hfq mutant and the wild-type Brucella strain led to the identification of numerous genes that require the HF-1 protein for its optimal expression during the stationary phase [3]. The products of these genes provide defences against various stresses in phagosome. An important enzyme shown to be regulated by HF-1 in the stationary phase of E. coli and S. typhimurium is Stationary phase survival protein, SurE and L-isoaspartyl protein carboxyl methyl transferase, Pcm. Genes for SurE and Pcm overlap and exist in an operon that is essential for the survival of E. coli and S. typhimurium in stressful condition

A fully formed biofilm now allows the individual bacterial cells to communicate with each other via quorum sensing. This activity helps cells pass information about their neighbors and surrounding environment to one

The review article chosen is titled, ‘Targeting of host organelles by pathogenic bacteria: a sophisticated subversion strategy’. It was published on the 23rd of November 2013 and written by Pedro Escoll, Sonia Mondino, Monica Rolando and Carmen Buchrieser of the Institut Pasteur in France. It explores how it has been discovered that bacterial pathogens have evolved to override normal eukaryotic cell behaviour in order to enter these cells and replicate, as well as shutting down the immune responses against these pathogens by reversing the roles of eukaryotic immune defence cells. The article itself is directed towards the scientific community,

The bacterial cell-to-cell communication process is referred to as quorum sensing (QS). Pheromones that act as cell-to-cell communicators are also called autoinducers (AIs), as they function to stimulate their own synthesis (Williams, Winzer, Chan, & Camara, 2007). AIs are produced and are continually released by bacteria at relatively low levels. The production, detection, and response of bacterial populations are determined by the concentration of the AIs. As binary fission occurs and the bacterial population density increases, there is an increase in the relative concentration of AIs in the nearby environment. As receptors bind to the AI, a quorum sensing circuit is initiated, and bacteria collectively alter gene expression for processes that benefit from collaborative action, such as: bioluminescence, sporulation, competence, biofilm adherence and formation, antibiotic