$Trichodesmium\, erythraeum$,which gives the Red Sea its characteristic red color,is a/an ........

Assertion: Gram-negative bacteria do not retain the stain when washed with alcohol.
Reason: The outer face of the outer membrane of Gram-negative bacteria contains lipopolysaccharides,a part of which is integrated into the membrane lipids.

In blue-green algae,photosynthesis is ........

Statement $S$: Methanogens are responsible for the production of methane. Statement $R$: They can survive even in acidic and high-temperature conditions.

Gram-negative bacteria detect and respond to chemicals in their surroundings by:

Those organisms which cannot use oxygen for growth and are even harmed by its presence are known as: