Microorganisms & its classification

Microorganisms & its classification, importance

Microorganisms which are organisms so small that Microorganisms cannot be seen with the naked eye. They can be observed only with the aid of a microscope. study of microorganisms called microbiology The ordinary brightfield microscope is mostly employed for routine microbiological work (microbiology work), though others like phase-contrast, darkfield, fluorescence and electron microscopes are also used.-medical microbiology notes

in this blog we well study about medical microbiology & human pathogens that caused diseasesand this blog also help you to prepare medical microbiology notes

Importance of medical microbiology-medical microbiology notes

• Microorganisms are found almost everywhere in nature. They are in constant interaction with human and other life cycles. Some bacteria, for example, are normal constituents of the human intestine.

• These microorganisms and their host benefit from such co-existence: The organisms derive food materials from the host, and some of the host's essential vitamins for existence are synthesised by the organisms.

• There are however certain microorganisms that are harmful to their hosts, that is, they can cause diseases. These microorganisms are known as pathogens. Those organisms that do not cause any harm are called commensals.

• This broad classification of microorganisms is not definitive because some commensals under certain conditions can become harmful to the host. The role of the medical microbiologist is to isolate and identify pathogens and develop effective ways to eliminate or control them.

• Isms into ordered groups based on biological relationship between them. Labelling of groups and of individual members within groups is known as nomenclature.  
• The whole process of classifying microorganisms is highly complicated and many workers have chosen to approach the topic from different perspectives. - Medical microbiology notes

Classification based on evolutionary (ancestry) origins is called phylogenetic classification, and that based on easily recognisable characteristics or features is called 'artificiall classification. 

Numerical taxonomy is a mathematical approach in which all features are given equal value. This is the original Adansonian concept. The advent of computers has made this approach to taxonomy easier to apply. Another concept that has found favour with many workers is the determination of the DNA base composition: members of the same species will have identical cellular DNA.

• In 1866, Haeckel proposed the establishment of a third and separate kingdom of living organisms, the Protista, which was defined to include algae, protozoa, fungi, viruses and bacteria. In 1957, Stanier divided the Protista into the eukaryotic (higher) and prokaryotic (lower) groups based on cell types.

• The eukaryotic cells which are found in protozoa, fungi, and algae, contain a nucleus bound by a nuclear membrane and undergo true mitosis. The prokaryotic organisms possess a nuclear structure of a single deoxyribonucleic acid (DNA) ring with no nuclear membrane. Table 1.1 shows the classification of the Protista. - medical microbiology notes

Biological classification methods provide the medical microbiologist with relatively simple ways for placing microbes into categories according to their morphological and biochemical properties. The word species is commonly used in this system of classification. 

• It is the basic unit in the hierarchy of microbial world. The basis of this category is that members of the same species are able to reproduce others of their kind.

• The next higher classification is the genus. The same genus comprises several species which may differ in several aspects. The genus of the microbe is usually abbreviated and the species written in full; it must start with a capital letter while the species starts with a small letter, e.g., Staphylococcus aureus is written as S. aureus.

• Further up the ladder of classification, micro-organisms with similar features are placed in successive larger categories Thus similar genera are grouped into families, similar families are categorized as order; similar order make up class; similar classes make up the phylum (Fig. 1.1).

• The wide and ever expanding variety of microorganisms has resulted in the break-up of Microbiology into separate specialized sections of Bacteriology (the study of bacteria), Virology (the study of viruses), Mycology (the study of fungi), Parasitology (the study of parasites) and lately serology immunology (the study of antigen/antibody reaction and immunity)

Bacterial classification system

There is constant arranging and re-arranging and renaming of microbes as new information is being discovered. 

• The reader is referred to Bergey's Manual of Determinative Bacteriology and the reports and publications of the International subcommittee on Taxonomy and Nomenclature for more and detailed information on this topic.

Classification of the Prostista

Some important human pathogens from various groups of microorganisms and diseases caused by them are listed in Table 1.2.

Human pathogens (BACTERIA)from various groups of microorganisms and diseases

BACTERIA - That caused diseases.

Human pathogens (VIRUSES)from various groups of microorganisms and diseases

VIRUSES- That caused diseases.

  Human pathogens(PARASITES) from various groups of microorganisms and diseases

PARASITES- That caused diseases.

  Human pathogens (FUNGI) from various groups of microorganisms and diseases

FUNGI- That caused diseases.