Non-Pathogenic (Useful) Microorganisms

Let us make an in-depth study of the non-pathogenic microorganisms. The below given article will help you to learn about the following things: 1. Microorganisms in Food 2. Microorganisms of Water 3. Microorganisms of Air 4. Industrial Microorganisms and 5. Nitrogen Fixing Microorganism and Life.

Microorganisms may be divided into two groups according to their activities:

(a) The useful and

(b) The harmful

The first group — the harmless, non-pathogenic microorganisms to man live mostly in the environment.

They are called as saprophytic or autotrophic (yeasts, moulds and bacteria) and are very useful to the industries for the manufacturing of alcohol, lactic acid, butter, cheese, solvents of paints and antibiotics etc. and to the agriculture to improve the soil fertility.

The second group — the harmful, may be called pathogenic microorganisms — damages the host and produces diseases in man, animals and plants. Out of 1,700 groups of bacteria, about 70 groups are patho­genic to man and can live only in human body, but they may die in external, unfavorable conditions.

The activities of useful microorganisms.

Decay, putrefaction and fermentation.

Decay is the term used generally to denote the gradual decomposition of organic matter (dead ani­mals, plants and their wastes) on or in the soil. Putrefaction is the decomposition of proteins (animal matter) under anaerobic conditions and of carbohydrates (vegetable derivatives starch or sugar).These two processes transform organic mat­ter into useful plant foods.

When dead animals and plants are buried in the ground, the soil micro flora and the intestinal micro flora of dead animal enter into the tissue of the animal or plant. Because of their lipolytic, proteolytic and saccharolytic activities, the microbes breakfast, proteins and sugars, respectively.

The gases (carbon dioxide and hydrogen sulfate etc.) liberated and water formed enter the air or soil. Besides, nitrogen, phosphorus, sulphur, produced from dead animal body combine with water and become’ soluble and suitable as food for plants.

Ultimately, the dead animal disappears. Later, the living animals and men use the plants as food. In this way, the recycle of the elements is continued. Thus, the life would be impossible on earth without microbial activity and the microbes are useful or essential for animal or hu­man life.

The coli bacillus and other species of mi­crobes in the healthy human intestine produce vita­mins (B₁, B₂, B₁₂, K) essential for the human body. Aci­dophilic microbes are beneficial to the human body as they interfere with the development of pathogenic bacteria which enter into the intestine along with food or drink.

It is well known that human beings cannot di­gest directly the cellulose of the plants and utilise it for their nutrition; but the rumen (stomach) micro flora of ruminants (cattle, sheep, goats) can only digest it anaerobically and convert into easily digestible end products like glucose, amino acids, volatile fatty ac­ids, which are excreted through milk or incorporated in animal tissue or muscle.

Man drinks milk contain­ing proteins, fatty acids and lactose which are de­rived from the cellulose of plant or green fodders digested by the rumen micro flora as the rumen of cattle is devoid of digestive enzymes. So the rumen micro flora are quite useful for human welfare with­out which milk or meat cannot be obtained from the animal for the human consumption.

Microorganisms in Food:

Moist less acidic foods (milk, cooked cereals, custard, soup) are suitable media for the growth of saprophytic and pathogenic microorganisms at warm room temperature and thus we consume large number of saprophytic microorganisms along with the foods every day with no harmful effects. The growth of certain microbes in some kinds of foods is useful.

Certain harmless streptococci added to cheese and butter may produce good flavours in them. There- fore, “starters”(materials containing the desired bac­teria) are added to the cream before it is churned into butter and they are also added to milk that is used for making the cheese. Flavour producing bac­teria (Lactobacillus) can ferment pickles.

Putrefaction is the anaerobic digestion and de­composition of proteins (muscle, egg white, fish) by microorganisms. It is usually accompanied by bad odour due to formation of ammonia, hydrogen sulfate and other volatile odoriferous substances.

Mostly, putrefied materials are not agreeable, but we con­sume the putrefied milk in the form of cheese and they are dangerous if contaminated. If foods are con­taminated with excessive growth of saprophytic mi­crobes, they are spoiled foods. This process is known as spoilage.

Fermentation:

Under anaerobic conditions, the microorganisms (bacteria, yeasts, moulds) decom­pose, by their saccharolytic activities, the carbohy­drates (sugars) into different kinds of acids, such as lactic acid, alcohol, and gases like carbon dioxide. One of the most familiar type of fermentation is the production of alcohol by yeast from the sugar of fruit juices as in wine manufacture. Certain streptococci (Streptococcus lactis) ferment sugar of milk (lactose) into lactic acid which causes souring of milk.

This harm­less streptococcus along with other saprophytic bac­teria enters into the milk from the dust, splits the milk if it is not refrigerated. The yeasts multiply in the dough and decompose the starch (sugar of the flour) and form alcohol and carbon dioxide. The gas bubbles entangled in the dough raise (leaven) the bread. The bread dries and becomes firm due to the evapora­tion of alcohol during baking.

The decomposition of fat by microorganisms is known as hydrolysis. When fats containing butyric and similar volatile fatty acids are decomposed, these ac­ids are liberated and are responsible for the odour and rancidity taste.

Pathogenic (harmful) bacteria may contaminate the foods or milk products, grow and liberate toxin (preformed toxin of Staphylococcus aureus and Clostridium botulinum) causing food poisoning. Sal­monella typhimurium (pathogenic to mice), when consumed along with the food, may also cause food poisoning in man in whom the illness takes the form of gastroenteritis. The food should be thoroughly cooked, kept closed in a vessel or should not be allowed to stand unrefrigerated and should not remain moist, as the moist food is a suitable medium for the growth of bacteria.

Application to Nursing:

Nurse must understand that the food should be protected from the microbes and should serve her patients and her own family with clean food.

Microorganisms of Water:

In ancient times and even now, in some back­ward community, the people throw the wastes of household out of window in the streets. These wastes and faeces may contaminate the community water supplies and thereby there will be great epidemics due to pathogens of intestinal tract: typhoid, cholera, gastroenteritis, hepatitis etc.

Modern microbiology utilizes concept of purifying sewage by the activities of certain saprophytic soil and water microbes and is of great importance to the community health in sup­plying purified water. The microorganisms utilise the organic substances of the sewage as food and turn them into harmless, inoffensive materials which are used as food by plants.

Municipal Sewage:

Method used for purifying municipal sewage is first straining out extraneous objects by passing the ‘raw’ (untreated) sewage through metal screens or racks, then allowing it to flow very slowly through large tanks. In such tanks, the solid matter in suspension settles to the bottom. This solid material is slowly decomposed through the hydrolytic action of microbial enzymes of anaerobic and facultative anaerobic bacteria. It eventually forms sludge (sort of mud) rich in plant food, which is pumped out, dried and used as fertiliser in garden. This sludge is sterilised before packaging.

The fluid part of sewage is sprayed on the sur­face of large beds (trickling filters) of coarse gravel. During this process, it becomes fully aerated. On the surface of gravel or sand a slimy film develops. This film consists of the growth of aerobic microorganisms, which get their nourishment by decomposing and oxidising offensive materials in the sewage as the sewage trickles slowly through the gravel. Solid mat­ter (humus) is collected in the final tank and pumped onto the open sludge drying beds. The deodorized, cleaned fluid is collected in drains under the gravel and run out in fields for irrigation.

Activated Sludge:

In modern activated sludge process, aeration of the sludge is accomplished by violently agitating the sewage with large volumes of the solid matter which is torn into small granules or particles. These particles contain millions of active aerobic microorganisms which use the air to oxidize and decompose rapidly the offensive matter in the sludge. Aeration is the key objective in any form of sewage disposal.

Drinking Water:

The waters of rivers, lakes, springs and oceans contain many saprophytic microorganisms; and these saprophytes are often present in drinking water and are harmless, since they cannot invade the human body. Man consumes large number of these saprophytes with food, water and milk every day. They are harmless.

However, water polluted with sewage usually contains pathogenic microbes (typhoid or dysentery bacilli, cholera vibrio’s, polio, hepatitis virus, amebae etc.). The only safe way is to boil all water or treat it with chlorine a few hours before use. Tablets of hypochlorite or other chlorine compounds are avail­able for this purpose. The nurse who is faced with the problem of disinfection of water at home can very well remember this method.

Microorganisms of Air:

Under ordinary conditions, the spores of numer­ous microorganisms may be found in air all around us. Many of these are spores of moulds, yeasts, useful conidia of streptomyces and spores of bacteria of the genera Clostridium and bacillus. Spores and conidia are excellently adapted to survive floating about on dust in the air for weeks or years.

All these spores are harmless except those of Clostridium and bacillus which are pathogenic to man. The number of micro­organisms in the air usually depends on the amount of dust since most of the microorganisms are riding around on dust particles. They are usually of the harm­less types found in soil and soon die in the dry air and sunlight. However, the air of badly ventilated dark room may contain many pathogenic organisms which are disseminated by the occupants who are carriers of such microbes in the nose and mouth.

In recent years much attention has been paid to the air as a means of disease transmission — espe­cially in hospitals. It is known that every drop of saliva and nasal exudate, even from healthy persons (nurses and doctors) contain microorganisms capable of caus­ing diseases. Among these, are staphylococci, pneumococci, streptococci of scarlet fever, puerperal sepsis, and septic sore throat, diphtheria bacilli, tuber­cle bacilli and numerous viruses (polio, influenza, ad­enovirus etc.)

Droplet Infection:

The air of class-room, theaters and street cars are loaded with microorganisms es­pecially in winter; sneezing and coughing sprays of saliva and mucus are added to the general popula­tion of the atmosphere laden by bacteria and viruses. Transmission of diseases by droplets of saliva and mucus is often called droplet infection. These sprays infect the dust and, when dry, this dust carries the bacteria.

Droplet Nuclei:

The droplets of saliva and dry mucus and the bacteria contaminated in the dried particles float in the air and are inhaled like dust. Such dried particles are spoken as “droplet nuclei” .These land on the floor, furniture’s, lips, hands, surgical wounds.

Application to Nursing:

Knowledge of microorganisms in the air will be useful to take precautionary measures, to protect herself and her patients from the microorganisms which sometimes may be pathogenic to man.

Industrial Microorganisms:

It is well established that the microorganisms produce alcohol, lactic and acetic acids during fer­mentation of carbohydrates; besides these products many other substances of equal importance are also formed. So, the microorganisms are widely used in industry.

The skill and knowledge of microbiologist, en­gineer and chemist are pooled together in the indus­trial fermentation to produce the large quantity of butyl alcohol, glycerin, antibiotics, vitamins and other substances of great importance depending upon the species of microorganisms.

In the manufacture of rubber, coffee, cocoa, tobacco, linen, spices, leather, pickles, drug and other products, the fermentative, putrefactive, synthetic and other enzymatic powers of microorganisms are utilised. Thus, it can be con­cluded that the microorganisms have entered in the business and became very useful to mankind.

Nitrogen Fixing Microorganism and Life:

Nitrogen is the component of the cytoplasm of the cell and is essential for the life. Though eighty per cent of the atmosphere contains nitrogen, the atmos­pheric nitrogen cannot be directly utilised by the liv­ing cell. But this nitrogen can be utilised from the atmosphere by the microorganisms by combining it with other elements, mainly oxygen, hydrogen and carbon of the atmosphere. The process of combining nitrogen of the atmosphere with other elements is called nitrogen fixation. The nitrogen of air can be fixed by certain soil microorganisms by two methods: non-symbiotic and symbiotic (living together for mutual benefit) nitro­gen fixation.

Non-Symbiotic Nitrogen Fixation:

The direct com­bination of atmospheric nitrogen as part of the proto­plasm of a living cell without the cooperation of any other organisms, e.g., atmospheric nitrogen can be built up directly into the protoplasm by the bacteria of the genus Azobacter (Azo = nitrogen), the genus Clostridium and other microorganisms.

These useful microorganisms are plenty in all the fertile soils. There- fore, a farmer permits the Azobaceter, Clostridium and other microorganisms to accumulate nitrogen from the air by allowing a field to lie fallow or unplanted. Nitrogen of the commercial fertilisers are very costly.

Symbiotic Nitrogen Fixation:

The nodules on the roots of leguminous plants (i.e., clover, beans, peas, alfalfa) contain bacteria belonging to the genus Rhizobium. While growing together with the plants, this genus Rhizobium collects nitrogen from the air and combines it into substances essential for the growth of both the bacteria and the plants. The process is known as symbiotic nitrogen fixation method.

Nitrification:

Nitrogenous compounds released into the soil by leguminous plants may be taken up by other plants and partly decomposed by putrefac­tion yielding ammonia (NH₃). As ammonia, nitrogen is generally useless to most green plants. Ammonia is also produced in small amounts by lightning flashes and is also washed into the soil by the rain. To be most readily available to plants, the nitrogen of ammonia must first be oxi­dised to nitric acid (HNO₃).

This important function is carried out by the soil bacteria of the family Nitro bacteriacae. The nitric acid they form immedi­ately combines with various substances to form nitrates. The process of changing nitrous acid into nitric acid is called nitrification.

These nitrifying bacteria and nitrogen fixing bacteria are of great importance to agriculture. The nitrogen of the air is useless to many microorganisms. At a depth of four feet (1.2 m), bac­teria become less numerous and at 10 to 12 feet (3- 3.7 m), there are usually no bacteria.

Microorganisms in and on Human Beings:

The healthy human body harbours millions of microor­ganisms on the skin, in the mouth, eyes, genitourinary tract and in the intestine and on every surface of the body which comes in contact with the outside of the world (air, food). Under normal conditions, most of the microorganisms do not produce the diseases, but under certain conditions (e.g., in wound or after sur­gery) gain entrance to the deeper parts of the body and produce the diseases.

The skin carries large number of bacteria. Sta­phylococcus aureus found in the hair follicles and sebaceous ducts causes the boils, carbuncles, breast abscess, infantile impetigo. The organisms lodged in the deeper layer of the skin cannot be removed by thoroughly scrubbing and then by the application of antiseptics, therefore sterile gloves are worn during operation.