Phi Kappa Theta Fraternity

Author : Md Saiful Islam | Published On : 18 Apr 2024

Phi Kappa Theta is a social fraternity with chapters and colonies in universities throughout the United States. It was founded in 1919 after the merger of two older fraternities: Phi Kappa and Theta Kappa. The sorority is centered on academics, service, and sisterhood.

The giant bacteriophage phKZ (phi kappa zeta) infects the bacterial species Pseudomonas aeruginosa and is highly resistant to bacterial immune enzymes. Recent research has found that phKZ assembles a nucleus-like shell after infection, which separates its DNA from host cytoplasmic proteins.

It Infects Pseudomonas aeruginosa

Pseudomonas bacteria exist naturally in wet environments like water and soil. You may even carry some on your skin without noticing, though you will not have an infection from this unless your immune system is compromised. This is why it is important to talk to your healthcare provider about staying clean and having a strong immune system.

People with weakened immune systems are at high risk for getting infections from Pseudomonas, including those with chronic pulmonary diseases such as bronchiectasis and cystic fibrosis, blood infections or invasive surgical procedures. Pseudomonas can also be spread from person to person via contaminated equipment.

Researchers have studied how phages can prevent Pseudomonas infection. In one study, Fu et al. pretreated hydrogel-coated catheters with a broad host-range phage and found a significant reduction in the number of P. aeruginosa cells in the biofilm after 2 h. However, a resurgence in the number of cells was observed after 24 h of treatment.

It Encloses Its DNA in a Nucleus-Like Shell

The nucleus is the organelle in eukaryotic cells that houses DNA and directs protein synthesis. It is surrounded by the nuclear envelope, which is comprised of two membranes. Each membrane has a phospholipid bilayer. There is a thin space between the membranes, which connects the nucleus to the interior of another membranous organelle called the endoplasmic reticulum. This space is punctuated with nuclear pores, which control the passage of ions, molecules and RNA between the nucleus and cytoplasm.

Prokaryotic cells have DNA, but it is not surrounded by a membrane like the nucleus. Instead, it is suspended in a semi-solid fluid called cytoplasm. This fluid contains dissolved proteins, enzymes and lipids. It is also where ribosomes are assembled.

To determine if the phikappazeta shell protects its DNA from bacterial immune enzymes, researchers tagged a Cas effector enzyme with a fluorescent dye and fused it to a phage-encoded protein that is capable of crossing the shell membrane. This fusion construct was then transfected into phKZ bacteria. They found that the presence of this fusion protein protected the bacteria from bacteriophage-induced lysis.

It Is Highly Resistant to Bacterial Immune Enzymes

Bacteria have evolved a couple of different strategies for self-defense against viruses. One involves immune enzymes that recognize foreign DNA and cut it up at specific locations called restriction sites. Another involves CRISPR-associated nucleases that target RNA transcribed by infected bacteria. phKZ and phages like it are highly resistant to both of these pathways, a team of researchers recently discovered. They figured this might be because the phage's shell protects its DNA from being recognized by bacterial enzymes. To test this, they isolated phKZ phage DNA from its virions and incubated it with immune enzymes such as Cas9 and the restriction enzymes EcoRI, HindIII, KpnI, and NcoI.

It Is a Giant Phage

The early research on phiKZ and the related giant phages made some surprising discoveries. For example, phiKZ-like phages are closely related to some potentially pathogenic bacteria, and their ability to transduce large bacterial DNA fragments in P. aeruginosa bacteria confirms the ability of these phages to transfer genetic information between different bacterial species.

In addition, the structure of phiKZ was studied and refined with modern methods of electron microscopy. The icosahedral head and contractile tail of the phage were shown to be much larger than previously thought. The phiKZ genome was also sequenced, which confirmed its unique characteristics and made it possible to classify it as a new phage family, the Ackermannviridae.

Further studies on phiKZ-related phages revealed their broad spectrum of lytic activity against P. aeruginosa and their ability to overcome the suppressing effect of some plasmids. These phages are capable of general transduction and pseudolysogeny. Their genomes are mosaic, which suggests high phage recombination and genetic exchange between phages.