2. General characteristics of microbes (Microbiology)

General characteristics of microbes for B.Sc. Nursing

1. Unit 2 General Characteristics of Microbes

2. Microorganism An organism is a living thing that ingests and break down food for energy and nutrient, excretes und ingested food as waste and is capable of reproduction. Microorganisms arc tiny organisms that live around us and inside our body. Microorganism are of two types, They are Pathogenic and Non-pathogenic microorganism

3. Pathogenic microorganism An infection is caused by the disease-causing microorganism known as a pathogenic microorganism. Some pathogenic microorganisms infect humans. but not other animals and plants. Some microorganisms that infect animals or plants also infect humans. Mycobacterium tuberculosis is the bacterium transmits infection through droplets of respiratory secretion or dry sputum from infected person lo uninfected person.

4. Non-pathogenic microorganism Non-Pathogenic microorganisms don’t cause disease but helpful in different ways. Some microorganism helps lo maintain homeostasis in human body and is used in the production of food and other commercial products. For example, flora is microorganisms found in intestines that helpful in the digestion of food and play role in formation of vitamins such as vitamin B and vitamin K. Moreover. it helps in breakdown of large molecules into small molecules.

5. Field of microbiology Microbiology are organized into six fields of study: Bacteriology Virology Mycology Phycology Protozoology and Parasitology

6. Classification of organisms Taxonomy Taxonomy is the science of organisms based on a presumed natural relationship. Scientist observe each organism, noting its characteristics. Organism that have similar characteristics are presumed to have a natural relationship and therefore are placed in the same group.

7. Cont … Carl Woese developed a new classification system that arranged organisms according to their molecular and then cellular characteristic. Eubacteria Eukarya Archaea

8. General characteristics of bacteria Bacteria are microscopic prokaryotic organisms whose cells lack a nucleus or nuclear membrane. The bacteria may found in different shapes. Bacteria have unique cell walls. reproduce by binary fission and exist in most environments on earth. Bacterial species vary in size. The smallest bacterium (Mycoplasma) are about 0.3 µm in diameter. approximately the size of the largest viruses (poxviruses). Escherichia coli bacterium of about 1.1 to 1.5 µm wide by 2.0 to 6.0 µm long. Most spherical bacteria have diameters of 0.5 to 2.0 µm and rod-shaped cells are generally 0.2 to 2.0 µm wide and 1- l0 µm long.

9. Classification of bacteria Bacteria are grouped by four main characteristics: Gram reaction: Gram + ve Gram - ve Shape: Atmospheric requirements: Obligate aerobes and anaerobes Facultative aerobes and anaerobes Capnophiles pH mediated (acidophile, alkaliphile, neutrophile ) Temperature mediated Endospores

10. Bacteria found in different shapes Cocci - Round or oval cells Bacilli - Rod shaped cells Spirilla - Non flexuous spiral forms Vibrio - Curved or comma-shaped rods Spirochetes- Slender and flexuous spiral forms Mycoplasma - Cell wall absent so bacteria found as round or oval cells Actinomycetes- Branched filamentous bacteria

11. Some bacteria are arranged in groups are Diplococci - Cocci arranged in pairs Streptococci - Cocci arranged in chains Staphylococci - Cocci arranged in clusters Coccobacilli - Both length and width are approximately same in the bacteria Streptobacilli - Bacilli arranged in chains Chinese letter or Cuneiform pattern - resemble like Chinese letter Tetrad - Cocci arranged as four cells Sarcina - Cocci arranged as cluster of eight cells

12. Bacterial motility In the most bacterial species, motility is the property of swimming by means of flagellar impulsion Bacteria flagellum contain filament which is rigid helix structure and the bacterium moves when this helix rotates. The direction of flagellar rotation determines the nature of the movement. To move forward flagella rotate counter clockwise (viewed from outside the cell). Whereas, cell itself rotate slowly clockwise. The bacteria can swim from 20 to almost 90 µm per second.

13. Flagella Flagella are threadlike locomotor appendages extending outward from the plasma membrane and cell wall. Most bacteria move with use of flagella is termed motility. Flagella are slender, rigid structure, about 20 nm width and up to 15 or 20 micrometer long. The detailed structure of a flagellum can only be seen in the electron microscope. The bacterial flagellum composed of three parts: Filament, Hook and B asal body

14. Types of flagella Monotrichous (single) One flagellum located at the end or pole A mphitrichous (on both side) S ingle flagellum at each pole L ophotrichous (tuft) C luster of flagellum at one or both ends P eritrichous (around) F lagellum that spread fairly evenly over the surface of the cell

15. Bacterial Endospore Endospore are small dehydrated metabolically quiescent forms that arc produced by some bacteria in response to nutrient limitation. Endospores develop within vegetative bacterial cells of several genera: Bacillus and Clostridium (rods) , Sparosarcina (cocci) and others. These structures arc extraordinarily resistance to environmental stresses such as heat, ultraviolet radiation, gamma radiation. chemical disinfectant and desiccation. These endospores produce resistance, because of this these considered as dangerous pathogen, they can often survive boiling for an hour or more.

16. Sporulation/ sporogenesis process Forms an axial filament of nuclear material Inward folding of the cell membrane to enclose part of the DNA and produce the forespore septum The membrane continues to grow and engulfs the forespore Cortex formation and both calcium and dipicolinic acid are accumulated Protein coats (exosporium) are formed around the cortex Maturation of the spores occurs like competition of coat synthesis, increase in refractility and heat resistance Transformation of dormant spore into active vegetative cells Activation Germination and Outgrowth

17. General characteristics of virus Viruses are strict intracellular parasite which live inside the other living cells. Viruses are simple forms contain biologically active particle that carry genetic information in either DNA or RNA molecules. Matured viruses, have nucleic acid covered with protein coat. Viruses lack the protein-synthesizing enzymes and structural apparatus necessary for replication. Replication is controlled by host cell. A virus is a set of genes, composed of either DNA or RNA, packaged in a protein containing coat. This particle is called a Virion.

18. Size and shape of virus Viruses are usually much smaller than bacteria and are submicroscopic. Most range of viruses is in size from 5 to 300 nanometers (nm). Some paramyxoviruses are up to 14,000 nm long. Animal viruses have many shapes, ranging from cubical, bullet-shaped, polygonal, spherical, filamentous or helical, to a complexed layered morphology. One of the most common morphologies of the viral capsid is, the Icoshedron . which consists of 20 triangular faces (capsomeres) that coalesce to form a roughly spherical structure enclosing the viral nucleic acid. Four common shapes of viruses are Helical, Polyhedral, Enveloped and Binal (complex) viruses.

19. Virus multiplication: Two possible outcome of a virus infection area productive or lytic response and non productive response also called Lysogeny. Absorption of the host cell Penetration or entry Uncoating to release the genome Virion component production Assembly Release from the cell

20. General characteristics of fungi Fungi arc eukaryotic microorganisms. About 200 species have been identified as human pathogens. The basic morphological structure of filamentous fungi is hyphae and a interconnected hyphae is called as mycelium. The cell walls of fungi consists of nearly 90% of carbohydrate (chitin, glucans, mannans) and fungal membrane are rich in sterols. Filamentous fungi reproduces either asexually (mitosis), by hyphae growth and tip extension or with the help of asexual spores. Molds grow in filamentous structures, yeast as single cells and dermatophytes cause infections of the keratinized tissues (skin, hair, nails, etc.).

21. General characteristics of parasite A parasite is defined as an organism that lives in a close association with another organism of a different species (the host) and is pathogenic to host. In medicine, the term is used in a narrow sense and denotes eukaryotic pathogens, which belong to the protozoa (unicellular organisms) and metazoan including helminths and arthropods. Protozoa are microscopic single celled eukaryotes superficially resembling yeasts in both size and simplicity. Helminths arc macroscopic, multicellular worms possessing differentiated tissues and complex organs system; they vary in length from a meter to less than a millimeter.

22. General characteristics of protozoa Protozoa are eukaryotic, single celled microorganisms about 1-150µm in size and enclosed by a cell membrane. They exist in almost every type of environment, over a wide range of pH (3 - 9.5), temperature and salinity. Reproduction is asexually by binary or multiple fission of the cell or sexual. Movement of the parasitic protozoa is by flagella, cilia or pseudopodia. Some species of protozoa produces resistant cysts and oocysts in which the parasite can survive outside of their host for longer periods. It receive nutrients by breaking down organic matter (heterotrophic) and can grow in both aerobic and anaerobic environments. such a protozoa that live in the intestine of animals.

23. General characteristics of protozoa It obtain food in one of the three way: Absorption, Ingestion and Engulf Protozoa can be subdivided into four main groups: Sporozoa (e.g., Microsporidium , Plasmodium , Toxoplasma ) Flagellates (e.g., Leishmania , Trypanosoma , Trichomonas ) Amoeboid (e.g., Entamoeba histolytica , Acanthamoeba spp .) Ciliates (e.g., Balantidium coli )