The bacteria are not always dangerous to mankind but there have various helpful bacteria which are quite useful for us.The Bacteria are exerting both useful and harmful effects on human being, these effects may be direct or indirect. Bacteria can be beneficial because it increases soil fertility, used in the treatment of sewage and other waste products, help in the preservation of food, produces some industrial chemicals as secondary metabolites. These types of beneficial bacteria may call as helpful bacteria. Some of the aspects helpful bacteria are enlisted below:
Increase in soil fertility (Agricultural helpful bacteria)
Bacteria are capable of fixing atmospheric nitrogen, this fixation are of different types. It can be by free living bacteria like Clostridium, Azotobacter. Symbiotic nitrogen fixation is most common in occurrence, which can be with legume plants e.g. Rhizobium legurninosarum or Psettdomonas radicicola or sometimes may be along with non-leguminous plant like Alder with Azospirillum. This activity enriches the soil with nitrogen and helps the plant to synthesize protein.
Bacteria in industry (Commercial helpful bacteria)
Bacteria are capable of producing various secondary metabolites, which have industrial importance or sometimes may be used in our day to day life. The industrial importance of bacteria may be as follows :
 Production of various dairy products: There may be different bacteria like Lactobacillus and Streptococcus, which are used in the preparation of fermented milk products like butter, cheese, curd and ghee.
 Production of alcoholic beverages: The preparation of different alcoholic beverages like wine and beer are done by the fermentation of malt or other plant polysaccharide by the acetic acid bacteria (Acetobacter).
 Production of organic acid: Different bacteria may be utilized in the preparation of different organic acids, which are as follows:
(i) Lactic acid : Helpful Bacteria like Streptococcus, Lactobacillus are utilized in the fermentation of complex carbohydrate to produce lactic acid, which can cause souring of milk.
(ii) Acetic acid : The production of acetic acid (vinegar) are carried out by the fermentation activity of Acetobacter acetii.
(iii) Butyric acid: Fermentation activity of Clostridium butyricum.
(iv) Propionic acid: By the fermentation of Propionibacterium.
(v) Minor Organic acids: like valeric acid, caproic acid are also produced by the fermentation of specific helpful bacteria.
 Production of amino acids : Production of amino acids like lysine is carried out by the fermentation activity of the bacteria Corynebacterium glutamicum.
 Production of Inorganic acid : Different inorganic acids like sulphuric acid are produced by the oxidation of elemental sulphur by the sulphur bacteria Thiobacillus. Nitric acid are produced by oxidation of nitrogen by nitrifying bacteria.
 Retting of fibres : Retting is actually decomposition activity of certain micro¬organisms, which helps in the separation of plant fibers in jute, flax, hemp etc. These helpful bacteria (e.g.Clostridium) grow under low oxygen content causing hydrolysis of the pectic substances that bind the fibers with the main stem. These fibers are commonly used in the manufacturing of ropes, canvas, carpets and other products.
 Curing and fermentation of tea and tobacco : The helpful bacteria like Bacillus megatherium and Micrococcus candisans are used in the curing and fermentation of tea and tobacco leaves, which is a part of their industrial processing.
 Tanning of leather and sponges : The process of tanning of leather and processing of sponges is carried out with the help of enzyme protease produced from the bacterium Bacillus subtilis.
 In paper and textile industry :The helpful bacteria Bacillus subtilis with the help of enzyme amylase help in the processing of textile and paper.
 In rubber and polymer industry : The bacteria Aerobacter is used in the manufacturing of synthetic rubber and various other polymers.
 Processing of coffee and cocoa seeds : The commercial processing of coffee and cocoa seeds are done by helpful bacteria like Erwinia and Bacillus.
 Production of gum and other allied products: The Xantham gum obtained from Xanthomonas campestris is actually an extracellular polysaccharide used as a gelling agent and also as an inhibitor for crystallization.
 Production of plastic : The plastic called Biopol is actually a derivative of Phenyl-hydroxy-butyrate obtained fromAlcaligenes eutrophus.
There have others helpful bacteria also. Click here for