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In this article we will discuss about the similarities of cyanobacteria with red algae and bacteria.
Similarities of Cyanobacteria with Red Algae:
(i) Flagellated or motile cells are absent in both cyanobacteria and red algae.
(ii) The blue (phycocyanin) and red (phycoerythrin) pigments occurring in cyanobactena are chemically similar to those occurring in red algae and are located on phycobilisomes in both groups.
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(iii) Both the groups have a common pattern of fatty acid formation which differs from other plants in that the lipid content does not increase as the thallus grows.
(iv) In both case, photosynthetic thylakoids occur singly and widely separated.
(v) In both case, the principle constituents of mucilage are sulfated galactoses, uronic acid, glucose, and xylose.
(vi) Pit connections are present in certain cyanobacteria and similar structures are also found in red algae
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(vii) In both cases, the major components in the cellulose are xylans, and trehalose and galactose occur in free form in both.
Similarities of Cyanobacteria with Bacteria:
(i) Both, bacteria and cyanobacteria are prokaryotes (i.e., they have nucleus without nuclear membrane, lack membrane-bound plastids, possess 70S ribosomes, lack histone proteins, lack cell organelles, peptidoglycan present in cell wall, etc.).
(ii) The mucilaginous sheath surrounding cyanobacterial cells and the capsule present in many bacteria possess a similar structure as both are made up of extremely fine fibrils.
(iii) Both are sensitive to antibiotics.
(iv) Both lack true sexual reproduction in which plasmogamy, karyogamy, and meiosis take place in a regular sequence at specified points during the life. Bacteria fulfill their requirements of sexuality by means of three processes (conjugation, transformation, transduction) of genetic recombination and these mechanisms have been reported in certain cyanobacteria (e.g., Anacystis nidulans).
(v) Many metabolic processes (e.g., sulfur and nitrogen metabolism) are similar in both groups.
(vi) Some bacteria also fix atmospheric nitrogen (e.g., Rhizobium, Azotobacter) which is an important function of most of the cyanobacteria.
(vii) Both possess certain structural similarities. For example, Thiothrix and some other bacteria are structurally similar to ‘hormogonia’ found in cyanobacteria; Beggiatoa, a sulfur bacterium, resembles with Oscillatoria in shape and movement.
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(viii) In both, cell wall and plasma membrane are connected at places.
