Pili in bacteria represent

Choose the correct names of the different bacteria given below according to their shapes.

In which of the following are gas vacuoles found?

The given characters are seen in which of the following group?
$(i)$ Unicellular,colonial,filamentous,symbiotic or free living.
$(ii)$ The colonies are surrounded by a gelatinous sheath.
$(iii)$ Some can fix atmospheric nitrogen in specialized cells called heterocysts.
$(iv)$ They often form blooms in water bodies.

Spirochaetes are ...

Eubacteria is an example of which domain?