|Another microsymbiont with nitrogen fixing capacity is Frankia having hyphal morphology similar to that of actinomycetes and produces nodules in woody non-legumes, like Alnus, Casuarina, Myrica , etc. It produces vesicles and sporangia in both free-living and symbiotic states. Azotobacter species are free-living (mostly root associated), aerobically nitrogen fixing bacteria. Nostoc, Calothrix, Gloeotrichia, Stigonema , etc are free-living aerobically nitrogen fixing Cyanobacteria. In addition, Vesicular Arbuscular Mycorhizae (VAM fungi) are free-living soil forms that increase nutrient uptake (specially by converting organic phosphorus into inorganic phosphorus), plant growth, nodulation and nitrogen fixation in legumes. In coastal areas of some countries, seaweeds are also used as biofertilisers. However, all these life forms may be grown artificially and inoculated in the soil as biofertiliser. The nitrogen fixers releases nitrogen during their life
time and also add other elements after their death and decay, essential for the growth of crops. The
biofertiliser also contributes organic matter and maintains a good soil texture. Azolla
contains well balanced amino acids and high amount of anthocyanine, a - carotene. These compounds also have positive effects on growth and yield of crops.
Large-scale production (2.5 m tons/year) of Rhizobium or Bradyrhizobium inoculants has been successful at several Universitis from Bangrladesh in India, to Costa Rica in Central America
About 1.5 to 2.0 kg inoculant/ha used with seeds may result increased production of pulses by 20 to 40%. Average Azolla production in a pond could be up to one m ton/ha/day, following the method developed at Botany Department, Dhaka University. It could also be grown along with irrigated rice crop. One cover of Azolla is about 10 m tons/ha and incorporation of two such covers could reduce urea-N fertiliser by about 50%. Azolla could also be made into compost and addition of about 10 m tons could supplement all
fertilisers by about 50%.
The benefits of biofertilisers over chemical fertilisers are manyfold. It is environmentally friendly, less expensive, increases soil organic matter, and believed to have growth promoting substances.
|Bacteria - a group of single-celled microscopic organisms without any organised nucleus. There are many forms of bacteria, the common being cocci (spherical), rods
(cylindrical) and spirals (cylindrical with twists around the long
axis). There are about 15,000 described species. In Bangladesh several
hundred species of bacteria are known. Although the general impression
about the bacterium as being a germ and hence harmful to man, is not
correct. The group has many useful attributes, and indeed the bacterial
world is critical in maintaining the biotic balance. Decomposition of
dead organisms into simpler organic compounds is essential for
recycling of organic matter, a job that is efficiently done by bacteria.
|The bacteria also are responsible for fixing the bulk of nitrogen from air
in a form that can be readily utilised by living organisms. Some
bacteria are particularly efficient in fixing atmospheric nitrogen and
in Bangladesh, species of Azotobacter and Clostridium fix atmospheric nitrogen directly. Bacteria such as Rhizobium form nodules in the root system of the leguminous pants and assist in
nitrogen fixation. Human intestine carries a large population of
bacteria, mainly Eschericia coli , Lactobacillus and Streptococcus ,
which provides both nutrients for the host and maintains proper
condition within the intestine for normal functioning. In cattle and
other livestock animals, the intestine houses special bacterial
communities that help in the digestion of cellulose, which is present
in large quantities in the grass, which these animals eat. Bacteria
also produce many essential drugs such as antibiotic and industrial
chemicals, and play important role in the fermented food industry.
Nevertheless, many dreadful diseases are caused by bacteria including plague , tuberculosis, sexually transmitted diseases such as syphilis and gonorrhoea, enteric illnesses such as cholera ,
bacillary dysentery, typhoid fever, and diseases of the respiratory
tract such as pneumonia, and infection of the brain (meningitis). In
Bangladesh it has been noted that Corynebacterium diphtheriae is responsible for diphtheria, Mycobacterium tuberculosi for tuberculosis, Vibrio cholera for Cholera, Diplococcus pneumoniae for pneumonia, Clostridium tetani for tetanus, and Salmonella typhosa for typhoid. In plants, the bacteria that cause disease include among others, Xanthomonas oryzae for bacterial blight of rice, Pseudomonas solanaceanum for wilting disease in tobacco and Xanthomonas citri
for citrus canker diseases in citrus plants. Of the numerous species of
bacteria, however, only a few, perhaps less than 5% of the species, are
actually pathogenic or disease forming.
|The Biology of Microorganisms and the scientific basis.
The basics of the science of Biology of Microorganisms
and its applications, as fertilizers and composting.