Microbes in Human Welfare 3

Question 1

biocontrol agents

Answer 1

*Biocontrol refers to the use of biological methods for controlling plant
diseases and pests.
*In agriculture, there is a method of controlling pests that relies on natural
predation rather than introduced chemicals.
*The use of biocontrol measures will greatly reduce our dependence on toxic
chemicals and pesticides.

Question 2

ladybird and dragon flies

Answer 2

1.Ladybird (Insect)-
*Beetle with red and black markings
*Useful to get rid of aphids

2.Dragonflies (Insect)-
*Useful to get rid of mosquitoes

Question 3

bacillus thuringiensis

Answer 3

e bacteria Bacillus
thuringiensis (often written as Bt) is used to kill butterfly caterpillars.

These are available in sachets as dried
spores which are mixed with water and sprayed onto vulnerable plants
such as brassicas and fruit trees, where these are eaten by the insect
larvae.

In the gut of the larvae, the toxin is released and the larvae get
killed. The bacterial disease will kill the caterpillars, but leave other insects
unharmed. Because of the development of methods of genetic engineering
in the last decade or so, the scientists have introduced B. thuringiensis
toxin genes into plants. Such plants are resistant to attack by insect pests.
Bt-cotton is on

Question 4

trichoderma

Answer 4

fungus Trichoderma. Trichoderma species are free-living
fungi that are very common in the root ecosystems. They are effective
biocontrol agents of several plant pathogens.

Question 5

Baculoviruses

Answer 5

Baculoviruses are pathogens that attack insects and other arthropods.

The majority of baculoviruses used as biological control agents are in the
genus Nucleopolyhedrovirus.

These viruses are excellent candidates for
species-specific, narrow spectrum insecticidal applications.

They have been shown to have no negative impacts on plants, mammals, birds, fish
or even on non-target insects.

This is especially desirable when beneficial
insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is
being treated.

Question 6

what are biofertilisers

Answer 6

there are problems
associated with the overuse of chemical fertilisers and there is a
large pressure to switch to organic farming – the use of biofertilisers.

Biofertilisers are organisms that enrich the nutrient quality of the soil.
The main sources of biofertilisers are bacteria, fungi and cyanobacteria.

Question 7

n2 fixing bacterial fertilisers

Answer 7

ou have studied about the nodules on the roots of leguminous plants
formed by the symbiotic association of Rhizobium. These bacteria fix
atmospheric nitrogen into organic forms, which is used by the plant as
nutrient. Other bacteria can fix atmospheric nitrogen while free-living in
the soil (examples Azospirillum and Azotobacter), thus enriching the
nitrogen content of the soil.

Question 8

fungal bertilisers

Answer 8

Fungi are also known to form symbiotic associations with plants
(mycorrhiza). Many members of the genus Glomus form mycorrhiza.
The fungal symbiont in these associations absorbs phosphorus from
soil and passes it to the plant. Plants having such associations show
other benefits also, such as resistance to root-borne pathogens, tolerance
to salinity and drought, and an overall increase in plant growth and
development

Question 9

cyanobacteria

Answer 9

Cyanobacteria are autotrophic microbes widely distributed in aquatic
and terrestrial environments many of which can fix atmospheric nitrogen,
e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria
serve as an important biofertiliser. Blue green algae also add organic matter
to the soil and increase its fertility. C