Which of the following is/are obligate intracellular parasites? a. chlamydia and rickettsiab. e. coli and pseudomonasc. mycoplasmad. treponema pallidum

Chlamydia and Rickettsia. (Ans. A)

Explanation:

Intracellular parasites are micro-parasites which are able to reproduce and grow inside the host cell.

Obligate intracellular parasites: They are the parasites that are not able to reproduce outside of their host cell, which means that the parasite is depending on intracellular resources for the reproduction.

Chlamydia and Rickettsia they both are two group of gram-negative bacteria. Chlamydia cannot make ATP and Rickettsia can make some ATP but not enough so they have to steal host ATP to live (survive). They have both DNA & RNA they can make their proteins.

Chlamydia site of replication is endosomes and transmitting from person to person and type of cell attack is columnar epithelium. Rickettsia site of replication is cytoplasmic and transmitting from arthropod vector and type of cell attack is endothelium.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.