General Characteristics of Microorganisms PDF

General characteristics of microorganisms  Introduction ❑ Microorganisms are the smallest organisms on Earth. In fact, the term microorganism literally means "microscopic organism.“ ❑ Microorganisms may be composed of prokaryotic or eukaryotic cells, and they may be si...

General characteristics of microorganisms  Introduction ❑ Microorganisms are the smallest organisms on Earth. In fact, the term microorganism literally means "microscopic organism.“ ❑ Microorganisms may be composed of prokaryotic or eukaryotic cells, and they may be single-celled or multicellular. Examples of microorganisms include algae, fungi, protozoa, bacteria and viruses. ❑ Microorganisms play many unique and complex roles within an ecosystem, and they can perform a variety of functions, such as photosynthesis, breaking down waste, and infecting other organisms.  Major characteristics of microorganisms Morphological characteristics: ❑ Cell shape, size and structure; cell arrangement; occurrences of special structures and developmental forms; staining reactions and motility and flagellar arrangement. ❑ Requires pure culture for study. ❑ Different types of microscopy can be employed for such characterization. Electron microscopy can help to see fine details of cell structure.  Major characteristics of microorganisms Chemical characteristics: ❑ The various constituents of microbial cells contain a wide variety of organic compounds. ❑ Microorganisms have characteristic chemical composition with both quantitative and qualitative differences. Example- occurrence of lipopolysaccharide in cell wall of gram negative bacteria. Basic distinction among viruses is made depending on the basis of the kind of nucleic acid they posses, namely, DNA or RNA.  Major characteristics of microorganisms Cultural characteristics: ❑ Nutritional requirements and physical conditions required for growth and the manner in which growth occurs. ❑ Different types of culture medium: Culture containing inorganic compounds or organic compounds (amino acids, sugar, vitamins etc). Complex substances like peptone, blood cells or serum) may also be needed. ❑ Some microorganisms require living host cells for growth. E.g.- ricketssias need a culture of mammalian tissues to grow. ❑ Incubation temperature is also very important. Some bacteria require more than 40ºC while others grow below 20ºC. Human pathogenic bacteria grow at body temperature, 37ºC. ❑ Presence or absence of oxygen and/or light also play important roles. E.g.- cyanobacteria uses light as a source of energy to grow.  Major characteristics of microorganisms Metabolic characteristics ❑ The process of metabolism of different microorganisms offer opportunities to characterize and differentiate many microorganisms. ❑ Some bacteria obtain energy by absorbing light while others oxidize inorganic or organic compounds. ❑ Microorganisms differ in ways in which they synthesize cell components during growth. ❑ The enzymes produced by different microorganisms may also vary significantly. Antigenic characteristics: ❑ Microbial cells contain specific antigens. ❑ Specific antibodies bind to specific antigens. ❑ Antibodies can therefore be used as tools for identification of specific microorganisms. ❑ Lock and key mechanism. Example - typhoid bacterium.  Major characteristics of microorganisms Genetic characteristics ❑ DNA of microorganisms contain constant and characteristic features which can help in their characterization. These are: DNA Base composition and the sequence of nucleotide bases in the DNA. ❑ The presence of plasmid DNA along with chromosomal DNA can add special characteristics on the cells containing them such as ability to make toxins or to become resistant to antibiotics or to use unusual chemicals as nutrients.  Major characteristics of microorganisms Pathogenicity ❑ The ability to cause disease is characteristic of microorganisms. ❑ Microorganisms can be pathogenic for animals, plants or plants and some can cause disease to other microorganisms too. E.g- viruses called bacteriophages can infect and destroy other bacterial cells. Ecological characteristics ❑ Habitat is an important parameter for characterization. ❑ Marine microorganisms are different than those living in fresh water environment. ❑ Microorganisms in the oral cavity are different to those of the intestinal tract.  Binomial Nomenclature ❑ Use Binary Names – Binary names (invented by Linnaeus), consisting of a generic name and a species epithet (e.g., Escherichia coli), must be used for all microorganisms. Names of categories at or above the genus level may be used alone, but species and subspecies names (species names) may not. In other words, never use a species name alone. ❑ When to Capitalize – The genus name (and above) is always capitalized, the species name is never capitalized, e.g. Bacillus anthracis ❑ When to Italicize - Names of all genus and species are printed in italics and should be underlined if handwritten (Bacillus anthracis); strain designations and numbers are not. If all the surrounding text is italic, then the binary name would be non-italic (Roman typeface) or underlined (e.g. A common cause of diarrhea is E. coli, a gram negative Coccobacilli).  Microorganisms and the Environment ❑ Microorganisms are found nearly everywhere. ❑ There are bacteria all over our skin, even on our eyelashes. ❑ A healthy human digestive tract depends on the help of particular microbes to break down and process the foods we eat. ❑ Microorganisms that contain chloroplasts and carry out photosynthesis, like algae and single-celled plants, process carbon dioxide and produce energy for themselves and most other life on Earth. ❑ Soil microbes break down plant and animal matter into smaller and smaller particles, eventually turning it into matter that other organisms can use as nutrients. ❑ Still other microbes are responsible for invading our bodies and making us sick. ❑ There are a wide variety of microorganisms, but they are all interested in one thing: reproducing. ❑ It just so happens that some of them make an impact on the world around them while they go about that task.