Joshua Lederberg and Norton Zinder discovered transduction, the process by which DNA is transferred from one bacterium to another by a virus, in 1952. This discovery was a landmark in bacterial genetics, demonstrating that bacteriophages could act as vectors for genetic material between host cells.
812
In what year were ultramicroscopic agents first identified as the cause of foot-and-mouth disease?
In 1898, Friedrich Loeffler and Paul Frosch demonstrated that the causative agent of foot-and-mouth disease could pass through porcelain filters that trapped bacteria. This discovery was significant as it provided the first evidence of a filterable agent, now known as a virus, being responsible for an animal disease.
813
What is the primary function of the cell wall in bacteria?
The bacterial cell wall is a rigid structure composed primarily of peptidoglycan. Its main biological function is to provide structural support and maintain the characteristic shape of the cell, while also protecting the bacterium from osmotic lysis in hypotonic environments.
814
How would you characterize the structural complexity of a bacteriophage tail?
The tail structure of many bacteriophages, such as the T4 phage, is highly specialized and complex. It consists of a contractile sheath, a base plate, and tail fibers. This intricate machinery is essential for recognizing specific host receptors, attaching to the bacterial cell wall, and injecting the viral genome into the host cytoplasm.
815
What is the term for viruses that are surrounded by a glycoprotein-containing envelope?
Enveloped viruses are those that possess an outer lipid bilayer membrane derived from the host cell, which is embedded with viral glycoproteins. These glycoproteins are crucial for the virus to interact with host cells, and the envelope itself makes the virus more susceptible to detergents and heat.
The realm Pararnavirae is a high-level taxonomic classification established by the International Committee on Taxonomy of Viruses (ICTV) to group viruses that utilize reverse transcription for their replication cycle, including retroviruses.
817
How many capsomeres are typically found in the capsid of a herpes virus?
The herpes virus capsid exhibits icosahedral symmetry and is composed of exactly 162 capsomeres. These capsomeres are organized into hexons and pentons, providing structural integrity to the viral particle and protecting the viral DNA genome within the host cell.
818
To which part of the bacteriophage structure is the tail assembly attached?
The bacteriophage virus is composed of a protein capsid, known as the head or head capsule, which contains the viral genetic material (DNA or RNA). The tail assembly, which is responsible for recognizing and injecting the genome into the host, is physically attached to the base of this head structure, forming a complex, organized viral particle.
819
How would you characterize the general size of a virus compared to other microorganisms?
Viruses are significantly smaller than bacteria, fungi, and protozoa. While bacteria are typically measured in micrometers, viruses are measured in nanometers. This small size is a defining characteristic that limits their structural complexity and necessitates their reliance on host cell machinery for replication.
820
What is the nature of the envelope found in viruses belonging to the order Rhabdovirales?
Viruses in the order Rhabdovirales, such as the rabies virus, are characterized by the presence of an outer envelope. This envelope is composed of a lipid bilayer derived from the host cell membrane, which is embedded with viral-encoded glycoprotein spikes. These glycoproteins are essential for the virus to attach to and enter host cells, facilitating the infection process.
