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explain the conditions needed for the growth of microorganisms
This varies depending on the type of bacteria. For example, warmblooded animal pathogenic bacteria require a temperature of around 98oF, a correct entry site, and for the host to be susceptible to that type of bacteria. [ Thermo-phillic bacteria require extremely hot temperature to grow. Viruses require a healthy host cell in order to get its DNA/RNA replicated. Parasites require the host body
to be healthy enough to sustain itself and the parasite. ]
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Asked 4/17/2012 7:19:28 AM
Updated 5/10/2013 4:11:49 PM
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Most micro-organisms require food, warmth, moisture, oxygen, time and a certain pH level in order to grow and multiply.

Moulds
•Most moulds are saprophytic i.e. they feed on dead organic matter. They grow on many foods especially fruit, bread, jam and cheese.
•Most moulds are mesophiles i.e. they thrive at temperatures between 20 and 45 degrees Celsius. Freezing (-18 degrees Celsius) inactivates mould growth. Temperatures below 15 degrees Celsius including fridge temperatures (1 to 4 degrees Celsius) retard mould growth. Cooking temperatures above 75 degrees Celsius destroy moulds.
•Moulds grow best in humid moist conditions, on foods with water present in liquid form. Frozen foods are unsuitable.
•Moulds are aerobic i.e. they require oxygen. As a result they grow on the surface of solid foods e.g. jam, and throughout open structure foods e.g. bread.
•Moulds favour slightly acidic conditions of pH 4 to pH 6. Extremely acidic or alkaline conditions inhibit mould growth.
•Moulds need time in order to multiply.

Yeast
•Yeast feeds on carbohydrates.
•Yeast thrives at temperatures between 25 to 30 degrees Celsius. Low temperatures inactivate yeast, while high temperatures of about 60 degrees Celsius kill yeast.
•Yeast needs moisture in order to grow.
•Yeast is a facultative organism i.e. it can live with or without oxygen.
•Yeast grows best in an acidic environment.
•Yeast needs time to grow.

Bacteria
•Some bacteria are saprophytic, and some are parasitic. Saprophytic bacteria i.e. those that feed on dead organic matter, include those bacteria which are present in soil and food and cause decomposition. Parasitic bacteria i.e. those that feed on living matter, cause diseases in humans, plants and animals.
•Bacteria have a very wide temperature range. Some are psychrophiles i.e. they thrive at low temperatures of -5 to 20 degrees Celsius, e.g. some clostridia bacteria.
Added 5/10/2013 4:11:49 PM
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identify common sources of infection
Weegy: he sources of infection are numerous, and for each type of infection a specific source becomes more significant than the others in the delivery of the infectious agent to the host, which is man in our discussion. [ The sources of infection can be divided into two main groups. These are exogenous and endogenous sources (3). A source of infection is endogenous when the infectious agent comes from the patient’s own body, usually from his own normal flora. Endogenous sources of infections become important when the person’s own immunity against his normal flora becomes compromised such as in cases of contamination during surgery, malnutrition, impairment of blood supply and debilitating diseases such as AIDS, diabetes or any other accompanying infection. Examples are the genera of staphylococci and streptococci which are normally found in the body, but can become pathogenic in certain circumstances (2). The exogenous sources of infection introduce organisms from any where outside to inside the body, which is the case most of the time. In addition to being exogenous, most of the time infections are transmitted from person to person or from animal to man (4). To be more specific, exogenous sources of infections can be either human, animal, or environmental in origin. Humans can be a source of infection in three cases, either when they are clinically infected (symptomatic infection), when they are asymptomatically infected or when they are carriers (5). ] (More)
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