Microbial world 2: Viruses

Question 1

How do viruses replicate

Answer 1

How virus reproduce:
In summary, viruses replicate by hijacking the machinery of living cells to produce more viruses. strategy of virus: enter a cell, take over its operations, produce new viruses, and then spread to other cells.

STEPS:

Attachment: Virus attaches to host cell via specific receptors, using viral surface proteins or glycoproteins for recognition. This specificity determines which cells or species the virus can infect.

Penetration: The virus enters the host cell either by endocytosis (engulfment by the cell) or fusion (merging with the cell membrane), depending on whether it’s enveloped or not.

Uncoating: The viral capsid (protein shell) disassembles to release the viral genetic material (DNA or RNA) into the cell, making it available for replication.

Replication and Transcription: The viral genome replicates using the cell’s machinery. DNA viruses might use host DNA polymerases, while RNA viruses may require viral RNA-dependent RNA polymerase (RdRp). Retroviruses use reverse transcriptase to convert RNA into DNA.

Translation and Protease Processing: The host’s ribosomes translate viral mRNA into proteins, which may then be processed by viral or host proteases to become functional.

Assembly and Maturation: New viral components assemble into immature virions, which mature into infectious viruses through structural changes, often within specific cell locations like the nucleus or cytoplasm.

Release: New viruses exit the cell, typically via lysis (cell bursting) for non-enveloped viruses, or budding (pinching off) for enveloped viruses, acquiring their membrane from the host cell.

Question 2

how are viruses observed using EM

Answer 2

Prepare the Virus: Get the virus particles ready, often by concentrating them from a fluid.

Fix It: Use chemicals to “freeze” everything in place, keeping the virus’s shape stable.

Dry It Out: Remove all water from the sample, because water can mess up the electron beam used to see the virus.

Embed (for TEM): For one type of EM, called Transmission Electron Microscopy (TEM), embed the virus in a special plastic to support it when slicing it into ultra-thin pieces.

Slice It Thin (for TEM): Cut the embedded virus into super thin slices, so thin that electrons can pass through.

Stain It: Apply heavy metal stains that electrons don’t like to pass through easily. This makes the tiny details of the virus more visible.

Look Under EM: Put the sample in the EM, and shoot it with electrons. These electrons interact with the sample, creating a detailed picture of the virus.

See the Virus: Analyze the images to see the shape, size, and other details of the virus

Question 3

HSV-1, HSV-2, VZV, HCMV, EBV, HHV-6, HHV-7, HHV-8

what do the following viruses have in common

Answer 3

all of these are from herpes family

Once infected, its for life bitch

n.b. HSV is herpes

Question 4

there are 2 types of electron microscopes;
* scanning EM
* transmission EM

which ones 3D?

Answer 4

SEMs provide a 3D image of the surface of the sample, whereas TEM images are 2D projections of the sample