Chair of Medical Biology, Microbiology, Virology, and Immunology

MICROBIAL ECOLOGY

Kuchmak O.B.

What is Microbial Ecology?

What is “Microbial”?

What is “Ecology”? – the study of the interactions between organisms and their environment

– of or referring to a minute life form; a microorganism, especially a bacterium that causes disease. Not in technical use.

Microbial ecology = The study of interactions between microorganisms and their environment (chemical, physical, and biological environment!)

In microbial ecology the main concepts are:

population - an elementary evolutional unit (structure) of a definite species;

biotope - site, habitation of a population, for parasites - place of their localization in an organism;

In microbial ecology the main concepts are:

microbiocenosis - microbial association, that is collection of populations of different species of microorganisms, which live in the defined biotope (for example, in an oral cavity, skin);

ecosystem - system, in which enters a biotope and microbiocenosis.

Types of symbioses:

Neutralism - the populations, existing in one biotope do not stimulate and do not oppress each other.

Mutualism exists when organisms live in an obligatory but mutually beneficial relationship.

Symbiosis - living together of two dissimilar organisms

The mutualistic association between rhizobia and N-fixing bacteria

Types of symbioses:

Commensalism - such relationship, at which the member called the commensal receives benefits, while its coinhabitant is neither harmed nor benefitted.

Types of symbioses:

Antagonism - oppression of one population another. The microbes – antagonists produce antibiotics, bacteriocines, fatty acids, which cause destruction of bacteria or delay their reproduction.

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Types of symbioses:

Parasitism - such kind of symbiosis, at which one population (parasite) brings harm to the host, and for itself has a benefit.

Ricketsia – intracellular parasites

• The soil is the major environment for a habitation of microorganisms.

• The amount of bacteria in one gram of soil can be very great - from 200 millions up to 10 billions

• The ground mass of bacteria is on depth 10-20 cm.

The microflora of soil includes hundreds of species of bacteria, viruses, protozoa, actinomyces and fungi. It is various species of putrefactiving, ammonifying, nitrifying, denitrifying, nitrogen-fixing bacteria, numerous iron bacteria and sulphur-bacteria. The most often inhabitants of soil are the representatives of genus Azotobacter, Nocardia, and Clostridium.

The role of microorganisms ?

producers consumers

decomposers

- the decomposition of pollutants and toxic wastes

the efficient utilization of limited natural resources

transformations of chemical substances that can

be used by other organisms

Help in

General microbial number (GNM) – quantity (amount) of all saprophytic bacteria in 1 g of soil is examined.

More exact rating is manufactured at definition coli - index, that is amount of bacteria E.coli in 1 g of soil.

The soil is considered pure, if its coli-index does not exceed 2000, and the quantity of termophilic bacteria is in limits 100 - 1000.

Escherichia coli, Streptococcus faecalis, Clostridium perfringens termophilic bacteria.

Sanitary - indicative bacteria of soil

A degree of fecal contamination of soil is determined on presence and quantity(amount) of first three species.

Soil Pathogens

Clostridium botulinum,

Clostridium tetanus,

Clostridium perfringens,

Bacillus anthracis

Water is a natural medium of a habitation of various microorganisms.

In sweet and salty waters representatives of all groups of bacteria are found Protozoa, Fungi, Viruses, Water - plant.

The microflora of reservoirs consists of two groups of microbes:

autochtonal (or aqueous) microorganisms / permanently live and are multiplied in water/. It is more often such species: Micrococcus candicans, M. roseus, Sarcina lutea, Bacterium aquatilis communis, Pseudomonas fluorescens. The anaerobes represent by species Clostridium, Bacillus cereus, B. mycoides.

allochtonal (brought from the outside).

The microbial composition of water is in the large degree mirrors a soil microflora. A major factor, which determines quantity of microbes in water is presence in it of necessary nutritious materials, that are various biological matters.

Main path of microbial contamination of water is penetration of unpurified waste from sewage of the populated area. Therefore, the more water is polluted with similar organic matters, there are more in it of microorga-nisms.

Zones of water clearnessPolisaprogenic zone is the zone of strong

contamination. It contains many organic matters and almost there is no oxygen. The quantity of bacteria in 1 ml of water reaches one million and more.

Mesosaprogenic zone is the zone of moderate contamination(pollution)). In it the nitrifying and aerobic bacteria prevails. The total number of microorganisms compounds hundreds of thousand in one ml.

Oligosaprogenic zone (zone of pure water). The quantity of bacteria changes from 10 up to 1000 in one ml.

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Sometimes the pathogenic bacteria in water can get and they will be saved for some time: Salmonella spp., S. typhi, V. cholerae, S. dysentеriae, L. interrogans.

Often various viruses are found: Polioviruses, Rotaviruses, Enteroviruses, Hepatitis A virus and others.

The pathogenic microorganism getting in reservoirs, abundant in a zone of strong contamination, gradually die in a zone of moderate contamination. They are almost not found in oligosaprogenic zones.

Common microbial number of water is examined by inoculation of 1 ml of water in melted and refrigerated up to 50 C in agar in Petri dishes.

Coli-index is determined by a method of membrane filters or fermentation tests.

Membrane filtration for determinging the coliform count in a water sample using vacuum filtration.

Enzymatic assay for coliform• Colilert system

• β-galactosidase of coliform

substrate ONPG → nitrophenol• β-glucuronidase of E. coli

fluorogenic substrate MUG

• Colilert system (for P-A test)

• β-galactosidase of coliform

substrate ONPG → nitrophenol (yellow)+Gal• β-glucuronidase of E. coli

fluorogenic substrate MUG

Microflora of air

Air for microorganisms is less favorable environment, than soil and water.

There are almost no the nutritious materials necessary for reproduction of bacteria. Desiccation and the ultraviolet rays operate perniciously on microorganisms.

Nevertheless, many microbes in air can be saved more or less long time.

Main sources of microbial air pollution is the soil, water and man.

The composition of a microflora of air is very various. It depends on cleanness of air, deposits, temperature, humidity, climate and geographical conditions. Than it is more in air of a dust, smoke, soot, the more micro-organisms.

Vice-versa, above mountains, seas, oceans and woods, where air is pure, it is not enough of microbes.

In open air spaces there are less of microbes, than in the closed rooms.

The constant microflora of air is shaped at the expense of soil microorganisms. In its composition many species of Actinomyces, Penicillinum, Aspergillus, Mucor and others go into. There are many Micrococcous roseus, M. candicans, M. luteus, Sarcina lutea, S. alba, S. rosea, Bacillus subtilis, B. mycoides, B. mesentericus.

Many microbial diseases are transmitted through the air during sneezing, coughing, or even normal breathing:

bacterial - tuberculosis, diphtheria, legionellosis, wooping cough, acute angine, epidemic meningitidis,

viral - influenza, measles, mumps, adenoviral infection

A sanitary - hygienic rating of air include

general microbial number sanitary - indicative microorganisms:

Streptococci haеmolyticus,

S. viridans,

Staphylococcus aureus.

Examination of air microflora is made according to

Koch’s sedimentation method Krotov’s aspiration method.