A bacterial cell consists of following components
Cell envelope It is the outer covering of protoplasm of
bacterial cell. It contains mucilage sheath, cell wall and
plasma membrane.
Cytoplasm It is a crystallo colloidal complex that forms
the protoplasm excluding its nucleoid. Membrane bound
cell organelles are absent. Cytoplasm along with nucleoid
are together called as protoplasm.
Nucleoid It represents the genetic material of
prokaryotes. Nucleoid consists of a single circular strand of
DNA duplex which is super coiled with the help of RNA
No nuclear envelope is present.
Plasmids These are self-replicating. extrachromosomal
segments of double-stranded, circular, naked DNA.
Flagella These are unstranded, equivalent to a single
microtubular fibre. These help in movement and
locomotion.
Pili and fimbriae Pili are longer, fewer and thicker
tubular outgrowths made up of protein pilin. Fimbriae are
small bristle-like fibres sprouting from cell surface in large
number. Pili are helpful in attaching to recipient cell and
forming conjugation tube. Fimbriae cause agglutination of
RBC. also help in mutual clinging of bacteria.

Archaebacteria are able to tolerate high temperature as
well as high acidity.
These bacteria are chemoautotrophic which obtain
energy for synthesis of food by oxidising sulphur. Under
anaerobic conditions they oxidise sulphur to sulphuric
acid.

Thermoacidophiles are able to tolerate high
temperature as well as acidity, due to the presence of
(i) branched chain lipids in the cell membranes.
(ii) special resistant enzymes capable of operating under
aerobic conditions.

(i) Paramylon These are found in euglenoids. These are
the products of photosynthesis which can be stored in
the cytoplasm.
(ii) Pseudoplasmodia These are found in slime moulds.
Pseudoplasmodia are formed when the food supply of
the medium is exhausted.
(iii) Heterocysts Present in cyanobacteria. They are the
sites of nitrogen-fixation.