Quorum Sensing in Bacteria

Quorum sensing is a sophisticated signaling mechanism employed by bacteria to regulate gene expression in response to population density. It enables bacteria to coordinate group behaviors, such as biofilm formation, virulence factor expression, and symbiotic relationships.

Key Components:

1. Autoinducers:
• Bacteria release small signaling molecules called autoinducers into their environment.
• Autoinducers accumulate as the bacterial population grows.
2. Receptor Proteins:
• Bacteria possess receptors that can detect the concentration of autoinducers.
• When the autoinducer concentration reaches a threshold (quorum), it binds to the receptors.

Function:

1. Gene Expression Regulation:
• Binding of autoinducers to receptors activates signal transduction pathways.
• This leads to changes in gene expression, influencing various cellular processes.
2. Coordination of Behaviors:
• Quorum sensing regulates behaviors that are more effective when executed by a population rather than by individual bacteria.
• Examples include the formation of biofilms, expression of virulence factors, and the establishment of symbiotic relationships.
3. Adaptation to Environment:
• Quorum sensing allows bacteria to adapt to changing environmental conditions collectively.
• It enhances survival and competitiveness in diverse ecological niches.

Examples:

• Vibrio fischeri: Bioluminescence in V. fischeri is controlled by quorum sensing, allowing the bacteria to emit light only when present in sufficient numbers.
• Pseudomonas aeruginosa: Quorum sensing regulates the production of virulence factors, contributing to the pathogenicity of this bacterium.

Applications:

• Understanding quorum sensing provides insights for controlling bacterial behaviours, offering potential strategies for disease control and biofilm management.

In conclusion, quorum sensing is a vital mechanism that allows bacteria to sense and respond to their population density, facilitating coordinated group behaviours essential for their survival and adaptation in diverse environments.

 

Gram Staining

 

Gram staining

Principle

When the bacteria is stained with primary stain Crystal Violet and fixed by the mordant, some of the bacteria are able to retain the primary stain and some are decolorized by alcohol. The cell walls of gram positive bacteria have a thick layer of protein-sugar complexes called peptidoglycan and lipid content is low. Decolorizing the cell causes this thick cell wall to dehydrate and shrink, which closes the pores in the cell wall and prevents the stain from exiting the cell. So the ethanol cannot remove the Crystal Violet-Iodine complex that is bound to the thick layer of peptidoglycan of gram positive bacteria and appears blue or purple in colour.

In case of gram negative bacteria, cell wall also takes up the CV-Iodine complex but due to the thin layer of peptidoglycan and thick outer layer which is formed of lipids, CV-Iodine complex gets washed off. When they are exposed to alcohol, decolourizer dissolves the lipids in the cell walls, which allows the crystal violet-iodine complex to leach out of the cells. Then when again stained with safranin, they take the stain and appear red in colour.

Procedure

1. Take a clean, grease free slide.
2. Prepare the smear of buttermilk or curd suspension on the clean slide with a loopful of sample.
3. Air dry and heat fix.
4. Crystal Violet was poured and kept for about 30 seconds to 1 minutes and rinse with water.
5. Flood the gram’s iodine for 1 minute and wash with water.
6. Then ,wash with 95% alcohol or acetone for about 10-20 seconds and rinse with water.
7. Add safranin  for about 1 minute and wash with water.
8. Air dry, Blot dry and Observe under Microscope.

Result

Violet coloured rod shaped gram positive  bacteria observed.

 

LAND DEGRADATION

The change in the characteristic and quality of soil which adversely affect its fertility is called as Degradation.

Land degradation means:

1. Loss of natural fertility of soil because of loss of nutrients.

2. Less vegetation cover

3. Changes in the characteristic of soil.

4. Pollution of water resources from the contamination of soil through which water sweeps into ground or runoff to the water bodies.

5. Changes in climatic conditions because of unbalanced created in the environment.

Causes of Land Degradation:

(a) Deforestation:Deforestation is taking place at a faster rate due to increasing demands of timber, fuel and forest products which results into degradation of land resources.

(b) Overgrazing:

Overgrazing refers to excessive eating of grasses and other green plants by cattle. It results into reduced growth of vegetation, reduced diversity of plant species, excessive growth of unwanted plant species, soil erosion, and degradation of land due to cattle movement.

(c) Agricultural practises:The modern agricultural practises, excessive use of fertilizers and pesticides has adversely degraded the natural quality and fertility of the cultivation land.

(d) Industrialization:

Development of industries for the economic growth of the country leads to excessive deforestation and utilization of land in such as way that it has lost its natural up gradation quality.

(e) Urbanization:Increasing growth of population and demand for more residential areas and commercial sectors is also one of the reasons for land degradation.

Prevention and Control Measures for Land Degradation:

Following are some practises for controlling land degradation:

1. Strip farming:

It is & practice in which cultivated crops are sown in alternative strips to prevent water movement.2. Crop Rotation:

It is one of the agricultural practice in which different crops are grown in same area following a rotation system which helps in replenishment of the soil.

3. Ridge and Furrow Formation:

Soil erosion is one of the factors responsible for lad degradation. It can be prevented by formation of ridge and furrow during irrigation which lessens run off.4. Construction of Dams:

This usually checks or reduces the velocity of run off so that soil support vegetation.

5. Contour Farming:

This type of farming is usually practiced across the hill side and is useful in collecting and diverting the run off to avoid erosion.

Land degradation is one of the world’s most pressing environmental problems and it will worsen without rapid remedial action. Globally, about 25 percent of the total land area has been degraded. When land is degraded, soil carbon and nitrous oxide is released into the atmosphere, making land degradation one of the most important contributors to climate change. Scientists recently warned that 24 billion tons of fertile soil was being lost per year, largely due to unsustainable agriculture practices. If this trend continues, 95 percent of the Earth’s land areas could become degraded by 2050.

 

LAND RESOURCES, LAND USAGE CHANGE

 LAND RESOURCES AND LAND USE CHANGE

The term “land resources” encompasses the physical, biotic, environmental, infrastructural and socio-economic components of a natural land unit, including surface and near-surface freshwater resources. Land resources include hills, valleys, plains, wetlands, river basins, etc. Throughout history humans have derived all the resources for human development and survival from land, such as food, water, fuel, agriculture, grazing, fishing , mining, etc. Industrial revultion is based on resources we get from land resources- Gold, iron, coal, diamond and oil.

LAND USE CATEGORIES

Major land-use categories are:

1. Forests: It is important to note that area under actual forest cover is different from area classified as forest. The latter is the area which the Government has identified and demarcated for forest growth. The land revenue records are consistent with the latter definition. Thus, there may be an increase in this category without any increase in the actual forest cover.
2. Land put to Non-agricultural Uses: Land under settlements (rural and urban), infrastructure (roads, canals, etc.), industries, shops, etc. are included in this category. An expansion in the secondary and tertiary activities would lead to an increase in this category of land-use.
3. Barren and Wastelands: The land which may be classified as a wasteland such as barren hilly terrains, desert lands, ravines, etc. normally cannot be brought under cultivation with the available technology.
4. Area under Permanent Pastures and Grazing Lands: Most of this type land is owned by the village ‘Panchayat’ or the Government. Only a small proportion of this land is privately owned. The land owned by the village panchayat comes under ‘Common Property Resources
5. Area under Miscellaneous Tree Crops and Groves (Not included in Net sown Area) : The land under orchards and fruit trees are included in this category. Much of this land is privately owned.
6. Culturable Waste-Land: Any land which is left fallow (uncultivated) for more than five years is included in this category. It can be brought under cultivation after improving it through reclamation practices.
7. Current Fallow: This is the land that is left without cultivation for one or less than one agricultural year. Following is a cultural practice adopted for giving the land rest. The land recoups the lost fertility through natural processes.
8. Fallow other than Current Fallow: This is also a cultivable land which is left uncultivated for more than a year but less than five years. If the land is left uncultivated for more than five years, it would be categorized as culturable wasteland.
9. Net Area Sown: The physical extent of land on which crops are sown and harvested is known as net sown area.

LAND USE CHANGES

Land use pattern changes mainly due to the following reasons:

1. Building homes

2. Developing industries

3. For making towns & cities

4. Making roads, railways, airports etc.

5. Building dams

IN-SITU & EX-SITU CONSERVATION

 CONSERVATION OF PLANT GENETIC RESOURCES

Plant genetic diversity is vulnerable to "genetic erosion", the loss of genes and alleles from populations, especially in locally adapted landraces. The replacement of local varieties with modern hybrid varieties and cultivars causes genetic erosion. This is intensified by the emergence of new pests, weeds, diseases, urbanization, and land clearing. 

There are two important methods of conservation.

1) In situ conservation

2) Ex situ conservation.

In situ conservation is the conservation of genetic resources at its original habitat as a natural population. An organism is conserved in the same area where it is naturally found. Examples are

Biosphere reserves, National parks, Wildlife Sanctuaries, and Biodiversity hotspots.

Biosphere reserves cover very large areas, more than 5000 sq. km. Currently, India has 18 BRs. Eg: Sundarbans (WB).

National Parks are regions that cover 100 to 500 sq. km. There are 103 NPs in India. Eg. Kaziranga- Assam- One Horned Rhino.

Wild Life Sanctuary- Aimed to conserve animal diversity, usually in small areas. There are 551 WLS in India. Eg- Aralam WLS - Malabar Civet.

Biodiversity hotspots - These are regions with at least 1500 vascular plants as endemics and 70% of the original habitat is lost. There are currently 36 hotspots all over the world, out of which 4 are in India. Eg: Eastern Himalayas, and Western Ghats.

Ex situ conservation

It is an 'off-site' conservation, in which an endangered species is protected outside its natural habitat, by removing or transferring the species from a threatened habitat. Botanical gardens, Zoos etc are examples. Lalbagh Bangalore, Royal Botanical Garden, Kew, etc.

Cryopreservation is another method of ex-situ conservation, in which seeds, pollen, tissues, and embryos are conserved in liquid nitrogen. 

Seed banks are also considered  as ex-situ conservation, in which dried seeds are stored in glass vessels or paper covers in a systematic manner.