A member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some which can cause disease
Any of various bacteria, living especially in fresh water, which obtain energy by oxidizing ferrous salts to insoluble ferric hydroxide.
Any of various bacteria of the suborder Rhodospirillineae and allied groups, which contain a purple photoactive pigment.
= tubercle bacillus.
A rod-shaped bacterium, especially Escherichia coli and members of the genus Aerobacter, found in the intestinal tract of humans and other animals. Its presence in water indicates fecal contamination and can cause diarrhea and other dysenteric symptoms