Viruses and Prokaryotes

Obligate Intracellular Parasite

An organism (like a virus) that requires a host cell's machinery and ATP to replicate.

Bacteriophage

A virus that specifically infects bacteria. Does not enter the cell; only injects its genome.

Positive-Sense RNA Virus

Viral genome that can be directly translated into proteins by the host ribosomes (acts just like mRNA).

Negative-Sense RNA Virus

Viral genome complementary to mRNA. Must carry RNA replicase in its virion to synthesize the readable strand before translation.

RNA Replicase

Enzyme that negative-sense RNA viruses MUST carry to synthesize a positive-sense mRNA strand.

Retrovirus

An RNA virus that carries Reverse Transcriptase to make a DNA copy of itself, integrating into the host genome (e.g., HIV).

Reverse Transcriptase

Enzyme carried by retroviruses to synthesize DNA from their RNA genome.

Viral Lytic Cycle

The virus maximizes the host's machinery to create new virions until the cell bursts (lyses).

Viral Lysogenic Cycle

The viral genome integrates into the host genome and replicates quietly; triggered by stress to enter the lytic cycle.

Provirus / Prophage

A viral genome that has successfully integrated into the host cell's DNA during the lysogenic cycle.

Horizontal Gene Transfer

The transfer of genetic material between bacteria, increasing genetic diversity without sexual reproduction.

Bacterial Transformation

A bacterium integrates naked genetic material from its surrounding environment.

Bacterial Transduction

Transfer of bacterial DNA from one bacterium to another via a viral vector (bacteriophage).

Bacterial Conjugation

The bacterial form of mating. Transfer of genetic material via a physical conjugation bridge (sex pilus).

Sex Pilus / F-factor

The physical bridge (pilus) and the specific plasmid (F-factor) required for bacteria to undergo conjugation.

Binary Fission

The method of asexual reproduction used by prokaryotes, resulting in two identical clones.

Peptidoglycan

The primary structural component of bacterial cell walls.

Gram-Positive Bacteria

Have a very thick peptidoglycan cell wall and stain deep purple.

Gram-Negative Bacteria

Have a thin peptidoglycan cell wall AND a lipopolysaccharide outer membrane. Stain pink.

Lipopolysaccharides

Found in the outer membrane of Gram-negative bacteria; triggers a severe, often dangerous immune response in humans.