Use the word bacterium when you're talking about a single celled organism. Your uncle's bad case of pneumonia might be caused by a bacterium.
A microscopic vegetable organism, belonging to the class Alg'91, usually in the form of a jointed rodlike filament, and found in putrefying organic infusions. Bacteria are destitute of chlorophyll, and are the smallest of microscopic organisms. They are very widely diffused in nature, and multiply with marvelous rapidity, both by fission and by spores. Certain species are active agents in fermentation, while others appear to be the cause of certain infectious diseases. See
Noun
(microbiology) single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered plants
n.
A microscopic vegetable organism, belonging to the class
Algae, usually in the form of a jointed rodlike filament, and found in
putrefying organic infusions. Bacteria are destitute of chlorophyll,
and are the smallest of microscopic organisms. They are very widely
diffused in nature, and multiply with marvelous rapidity, both by
fission and by spores. Certain species are active agents in
fermentation, while others appear to be the cause of certain infectious
diseases. See Bacillus.
Bacterium
A microscopic vegetable organism, belonging to the class Alg'91, usually in the form of a jointed rodlike filament, and found in putrefying organic infusions. Bacteria are destitute of chlorophyll, and are the smallest of microscopic organisms. They are very widely diffused in nature, and multiply with marvelous rapidity, both by fission and by spores. Certain species are active agents in fermentation, while others appear to be the cause of certain infectious diseases. See
Usage Examples
Bacterium, Bacterium, acterium, Bacterium, Bqacterium, Bwacterium, Bsacterium, Bzacterium, Bqcterium, Bwcterium, Bscterium, Bzcterium, Baqcterium, Bawcterium, Bascterium, Bazcterium, Baxcterium, Badcterium, Bafcterium, Bavcterium, Ba cterium, Baxterium, Badterium, Bafterium, Bavterium, Ba terium, Bacxterium, Bacdterium, Bacfterium, Bacvterium, Bac terium, Bacrterium, Bac5terium, Bac6terium, Bacyterium, Bacgterium, Bacrerium, Bac5erium, Bac6erium, Bacyerium, Bacgerium, Bactrerium, Bact5erium, Bact6erium, Bactyerium, Bactgerium, Bactwerium, Bact3erium, Bact4erium, Bactrerium, Bactserium, Bactderium, Bactwrium, Bact3rium, Bact4rium, Bactrrium, Bactsrium, Bactdrium, Bactewrium, Bacte3rium, Bacte4rium, Bacterrium, Bactesrium, Bactedrium, Bacteerium, Bacte4rium, Bacte5rium, Bactetrium, Bactefrium, Bacteeium, Bacte4ium, Bacte5ium, Bactetium, Bactefium, Bactereium, Bacter4ium, Bacter5ium, Bactertium, Bacterfium, Bacteruium, Bacter8ium, Bacter9ium, Bacteroium, Bacterjium, Bacterkium, Bacteruum, Bacter8um, Bacter9um, Bacteroum, Bacterjum, Bacterkum, Bacteriuum, Bacteri8um, Bacteri9um, Bacterioum, Bacterijum, Bacterikum, Bacteriyum, Bacteri7um, Bacteri8um, Bacteriium, Bacterijum, Bacteriym, Bacteri7m, Bacteri8m, Bacteriim, Bacterijm, Bacteriuym, Bacteriu7m, Bacteriu8m, Bacteriuim, Bacteriujm, Bacteriunm, Bacteriujm, Bacteriukm, Bacteriu,m, Bacteriu m, Bacteriun, Bacteriuj, Bacteriuk, Bacteriu,, Bacteriu , Bacteriumn, Bacteriumj, Bacteriumk, Bacterium,, Bacterium .