Question

Which one is not a characteristic feature of cyanobacteria?
(a)They are always multicellular
(b)They form colonies
(c)They form bloom in polluted water bodies
(d)They can fix atmospheric nitrogen.

Answer 1

Cyanobacteria, is a group of prokaryotic organisms, commonly known as blue-green algae. Most members are filamentous forms, but some are unicellular.

Complete step by step answer:
Members of Cyanobacteria are mostly filamentous, although unicellular and colonial forms also occur. So they are not always multicellular. In filamentous forms, cells attach the end to end and get embedded in a gelatinous sheath, forming a ribbon. But in colonial form cells adhere together and form a flat or spherical colony. It consists of both free-living photosynthetic bacteria and the endosymbiotic plastids, the autotrophic eukaryotes that include the red and green algae and land plants. They commonly obtain their energy through oxygenic photosynthesis. They appear to have originated in freshwater or a terrestrial environment. Blue-green algae differ from all the other algae by virtue of their Prokaryotic cellular organization. Their cells are primitive and usually larger than the bacterial cells. They reproduce only asexually by simple cell division, spore formation, and fragmentation.

So, the correct answer is ‘They are always multicellular'.

Additional information: -All cells have a gelatinous sheath that contains pigments and toxins. Pigments are not localized in definite chromatophores but are confined to peripheral portions of protoplasm.
-Flagella are completely absent. The food reserve includes Cyanophyceae starch and Cyanophyceae granules.
-Cell walls have two layers, an outer layer containing thick gelatinous sheath, formed of pectic compounds, and an inner cellulose layer.

Note:
-Most blue-green algae are photosynthetic. They carry out oxygenic photosynthesis, releasing oxygen.
-A number of species have the capacity to change their color in relation to the wavelength of the incident light.
-The change in color is often referred to as complementary chromatic adaptation or the Gaidukov phenomenon.