Bacteria are not

a complete nuisance to man, because they have many beneficial effects in agriculture, medicine, industry, and research.
*Help in decay of organic substance reducing them to simple form such as nitrates, sulphates and phosphates. Thus increasing soil fertility.
*Nitrification, in which proteins in dead plants and animals are converted into ammonium compound and oxidized to nitrate and nitrate available for plants.
 *Nitrogen fixation  in which atmospheric nitrogen is fixed by N-fixers like Azotobacter, Clostridium and Rhizobium.
 *Fertilizer production in which cow dung, animal excreta are converted into manures, and formation of humus are due to action of bacteria.
 *Eubacteria in the intestine sythesize vitamins absorbed by the body which aid in digestion of certain materials.
 *In industry, manufacturers use cultured bacteria to synthesize some compounds such as acetic acid (vinegar) by Acetobacter, Aceti, Acetone, butanol, lactic acid by lactobacillus and several vitamins.
 *Bacteria used in retting of flax and hemp for use in making linen and other textile and rope.
 *Commercial preparation of skin for making leather goods.
 *In making diary products such as butter and cheese.
 *Curdling of milk by lactic acid bacteria.
 *Making silage for cattle feed.
 *Bacteria pathogenic to certain insect may be used as control methods to replace insecticides.
 *Production of antibiotics, such as streptomycin, aurcomycin, terramcin, neomycin which are derived from species of actinomyces.
 *Genetic engineering research e.g E coli
 *production of certain enzymes and other substances e.g insulin
 *Intestinal balance of bacterial flora is essential for normal health.
The above importance of bacteria simply suggests that in as much as they pose harmful to man, they have many advantages.