Bacteria, Virus, Prion, and Protist

Bacteriophages, or bacteria, are viruses that attack the cell. Most bacterial walls contain peptidoglycan, which consists of polymers of modified sugars cross-linked by short polypeptides that vary from species to species. Gram stain can determine whether the bacteria is gram-positive or gram-negative. A gram-positive bacteria is when the cell walls has a big amount of peptidoglycan. A gram-negative bacteria has less peptidoglycan but more lipopolysaccharides, carbonhydrates bonded to lipids. Pathogenic gram-negative bacteria is often more harmful because their lipopolysaccharides may be toxic and this outer membrane also protects them. Bacteria reproduce asexually by binary fission, which is cell division which synthesizes DNA continually, producing a colony of progeny. There are three basic genetic recombination for bacteria: transformation, conjugation, and transduction. Transformation is the uptake of genes from the environment. Conjugation is the direct transfer of genetic material between prokaryotes. Transduction occurs when the virus transfers the gene. Endospores in bacteria allow the bacteria to thrive in harsh conditions, such as boiling temperature or hydrate and revive to the cology-producing state.
Viruses are noncellular parasites that attack cells. Because they are obligate intracellular parasites, they must wait for the right moment to penetrate and enter the cell, claiming its new host. Viruses can undergo either lytic cycle or lysogenic cycle. Three main important parts of the virus is its tail, DNA/RNA, and protein coat.
A prion is a protein infectious agent that does not reproduce by itself and may be linked to several degenerative brain diseases. Unlike the bacteria and virus, the protist is an eukaryotic organism. It is not like the bacteria and virus where it penetrates the host and causes the host to be sick.
A protist is a unicellular eukaryote, single-celled, and microscopic. A protist has multicellular forms and some relatively complex giants. The main groups of Protistan diversity are Diplomonadida, Parabasala, Euglenozoa, Alveolata, Stramenopila, Rhodophyta, Chlorophyta, and Mycetozoa. Some examples of protists include the Paramecium and the Euglena.

Bacteria

Virus

Protist-Paramecium

Protist-Euglena

Source: Campbell book
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