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2 years ago

Why are some pathogenic bacteria able to make toxins?

1 answer:

6 0

A pathogen is a microorganism that is able to cause disease in a plant, animal or insect. Pathogenicity is the ability to produce disease in a host organism. Microbes express their pathogenicity by means of their virulence, a term which refers to the degree of pathogenicity of the microbe. Hence, the determinants of virulence of a pathogen are any of its genetic or biochemical or structural features that enable it to produce disease in a host.

The relationship between a host and a pathogen is dynamic, since each modifies the activities and functions of the other. The outcome of such a relationship depends on the virulence of the pathogen and the relative degree of resistance or susceptibility of the host, due mainly to the effectiveness of the host defense mechanisms. Staphylococcus aureus, arguably the most prevalent pathogen of humans, may cause up to one third of all bacterial diseases ranging from boils and pimples to food poisoning, to septicemia and toxic shock. Electron micrograph from Visuals Unlimited, with permission.

The Underlying Mechanisms of Bacterial Pathogenicity

Two broad qualities of pathogenic bacteria underlie the means by which they cause disease:
1. Invasiveness is the ability to invade tissues. It encompasses mechanisms for colonization (adherence and initial multiplication), production of extracellular substances which facilitate invasion (invasins) and ability to bypass or overcome host defense mechanisms.

2. Toxigenesis is the ability to produce toxins. Bacteria may produce two types of toxins called exotoxins and endotoxins. Exotoxins are released from bacterial cells and may act at tissue sites removed from the site of bacterial growth. Endotoxins are cell-associated substance. (In a classic sense, the term endotoxin refers to the lipopolysaccharide component of the outer membrane of Gram-negative bacteria). However, endotoxins may be released from growing bacterial cells and cells that are lysed as a result of effective host defense (e.g. lysozyme) or the activities of certain antibiotics (e.g. penicillins and cephalosporins). Hence, bacterial toxins, both soluble and cell-associated, may be transported by blood and lymph and cause cytotoxic effects at tissue sites remote from the original point of invasion or growth. Some bacterial toxins may also act at the site of colonization and play a role in invasion. Acid-fast stain of Mycobacterium tuberculosis, the agent of tuberculosis (TB). The bacteria are the small pink-staining rods. More than one-third of the world population is infected. The organism has caused more human deaths than any other bacterium in the history of mankind. Although its ability to produce disease is multifactorial, it is not completely understood. American Society of Microbiology, with permission.

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Which one is NOT one of the properties of water?

marysya [2.9K]

Answer:

a. the frozen form is more dense than the liquid form

Explanation:

The remaining properties are exhibited by water and are described as follows.

b. the frozen form is less dense than the liquid form

1. Water freezes to form ice.

2. When ice is put in water, ice starts floating in water and is visible.

3. If the density of ice was greater than water, ice would have got sunk and go downwards in the water body.

4. Hence, ice which is frozen form of water, has less density than water.

c. water is a solvent

1. The solvency is defined as the ability of a liquid to dissolve a substance.

2. Water is called the universal solvent. This means water can dissolve almost all types of substances.

3. Water is a polar solvent. The polar water molecules have the ability to break down both ionic and covalent bonds.

d. water has a high heat capacity

1. This is defined as the amount of heat needed by 1 gram of a substance so that its temperature is changed by 1 degree centigrade. The heat can either be gained or lost for the temperature to change.

2. The heat required by 1 gram of water to either increase or decrease the temperature of water is called the heat capacity of water.

e. water has a high heat of evaporation

1. This is defined as the amount of heat needed by 1 gram of a substance so that it changes its state from liquid to gas.

2. The heat required to convert 1 gram of water into vapours is called the heat of evaporation of water.

3. 1 g of water when heated at 25 centigrade needs 580 calories of heat to convert into gas.

All the above properties of water show the importance of water for life.

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3 years ago

4. Monosaccharides are to polysaccharides as

vova2212 [387]

Answer:

Explanation:

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3 years ago

- Describe what happens to a fertilised egg cell before implantation in the uterus.

dangina [55]

Answer:

During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, the morula becomes a blastocyst. The blastocyst then burrows into the uterine lining — a process called implantation.

Explanation:

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3 years ago

1. Compare the average global temperatures from the early 1900’s and the early 2000’s. How has the

sveticcg [70]

1. The average global temperatures from the 2000’s early are higher than those from the early 1900’s. We can see from the diagram that the average global temperature in the 1900s was about 57 degrees Fahrenheit (13.8 o C). In the 2000s the temperature raised to more than 58 F (about 14.5 o C). The world temperature is increasing due to human activity or natural variability. Some of the causes of this global warming are: burning of fossil fuels, agriculture , deforestation all leading to greenhouse effect.

2. Carbon dioxide (CO2) is naturally present in the atmosphere as part of the carbon cycle, but its amount is raised due to human activities. This gas is produced by the process of burning fossil fuels (coal, natural gas, and oil), solid waste, trees and wood products..CO2 is removed from the air by the absorption of the plants or it dissolves into the ocean over a period of 20–200 years.

Methane is produced during the production and transport of coal, natural gas, and oil. It is removed from the atmosphere by chemical reaction, persisting for about 12 years.

Nitrous Oxide (N2O) is formed during agricultural and industrial activities or during the burning of fossil fuels and solid waste.N2O is destroyed in the stratosphere persisting for around 114 years.

Fluorinated gases such as hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride are formed in different industrial processes. Those gases have long atmospheric lifetimes sometimes thousands of years.

3. Greenhouse gases such as CO2, N2O, fluorinated gases, methane are gases that trap the heat in the atmosphere, causing the warmer climate. The amount of a particular greenhouse gas in the atmosphere can be measured. Higher emissions of those gases lead to higher concentrations in the atmosphere. Because of the Industrial Revolution , atmospheric greenhouse gas amount is raised for the last century and that increased the global average temperature.

4. There are many ways for reducing the amount of CO2. Some of them are:

• Reduce Vehicle Emissions, since the use of vehicle for transport is one of the largest sources of this greenhouse gas. Drive a bike, get a gas-efficient vehicle or a hybrid car.

• Reduce Home Energy Carbon Emissions by insulating and sealing your home, turning off lights, add solar panels to the roof of your home etc.

5. Solar energy that travels to the Earth is absorbed by the its surface and converted into heat, which is released into the atmosphere. The greenhouse gases such as carbon dioxide (CO2) absorb that heat and send it back to the Earth's surface. This process is known as the greenhouse effect and it leads to temperature increase. This happens because the increase in greenhouse gases in the atmosphere trap too much heat.

6. Since the greenhouse gases trap the heat, if there were less of those gases, much of the infrared radiation (solar energy) that is converted to heat today would not be trapped in the Earth's atmosphere. The temperature of the Earth would cool down, and a conditions of the Ice Age would occur. These conditions would be very unfavorable for plants and animals, oceans would freeze, and weather patterns would change.

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3 years ago

A region has mostly dark colored soil, but a small patch of light-colored soil creates a microclimate. Which of the following is

Ivenika [448]

Lower temperature than the surrounding climate due to the soil being lighter it doesn’t take in as much heat

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3 years ago