Lecture 1 Flashcards
What is Microbiology
study of microscopic organisms also known as microbes
four major groups of microorganisms(morgs)
Viruses
Bacteria
Fungi
Parasites(protozoa and metazoa)
Branches of Microbiology
Industrial Microbiology Agricultural Microbiology Sanitary Micro Veterinary Micro Medical/Clinical Micro
Medical microbiology
study, identification and the control of microbes which can cause disease in humans
microbes which can cause disease in humans
Pathogens
Illness caused by pathogens is termed
infection or infectious disease
four major disciplines:
Bacteriology: the study of bacteria
Mycology : the study of fungi
Parasitology : the study of parasites
Virology : the study of viruses
Viruses
Are non-cellular particles
They are the smallest ,ranging in size from 0.01 to 0.3 µm (10-300 nm) They are observed only through an electron microscope
May not be living
Consists of a genomic core of DNA or RNA but never both,and a coat of protein around the core known as envelope
Produce progreny in host
No independent reproduction
Obligate intracellular parasites
Bacteria:
They are prokaryotic microbes 2 to 6 µm in size.
Unicellular can reproduce independently by binary fission
Divide by fission- form colonies
Are able to live independently in nature, in the soil, water, on plants, animals and humans when live as companions with the humans known as Normal flora
When cause disease in humans known as pathogens
Most bacteria are free living or parasitic forms that can metabolize and reproduce by independent ways.
Fungi
They are eukaryotic 2.0 to 100 µm in size
They are unicellular and multicellular
Unicellular-Yeast
Multicellular- molds,dimorphic fungi (Pathogenic fungi) Candida ( opportunistic pathogens)
Have all organelles found in human cells
Protozoa
Most protozoa are single celled
They are eukaryotic
5.0 to 200 µm
They are motile by pseudopods ,flagella or cilia.
Are free living or live inside the human body for part of their life cycle
E.g amoeba
General size of microorganisms
Amoeba = 15 µm Yeast = 5 µm Bacteria = 2 µm Virus = 0.1 µm( 100 nm) So, amoeba >yeast>bacteria>virus
Unusual forms of medically significant bacteria
Rickettsias, Chlamydias, Spirochetes
The rickettsias and chlamydias, however have adapted to life inside their host cells.
Eg.Chlamydia tracomatis
Therefore, are considered obligate intracellular parasites
capsule:
it is a slime layer found in some bacteria outside the cell wall, not easily washed off, and,
Allows these microbes to resist phagocytosis by WBCs and increases the virulence (disease causing capacity ) eg.E.coli, Klabsiella pnemoniae,Haemophilus influenza
Cell wall
it is a unique prokaryotic feature, resists shrinkage of the cell.
Bacterial cell walls gain their rigidity from a unique macromolecule called peptidoglycan.
one of the major basis for the classification of the bacteria. Gram positive and Gram negative cell walls are chemically different
Cell membrane
it is a semi-permiable organelle ,which allows material in and out of the cell
Flagella
they are whip like hairs/tails helps in the motility of the bacterium
Pili/Fimbriae
are small hair like projections on the surface, allow bacteria to stick to the surface and also used to
move DNA plasmids between bacteria
Plasmid
It is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA.
They are double-stranded and, in many cases, circular. Plasmids usually occur naturally in bacteria.
Plasmids are responsible for the antibiotic resistance .
Bacterial growth
Growth is the term applied to the process of increasing the number of bacteria.
Bacteria grown in the lab are referred to as a culture
Conditions for growth
Temperature,moisture osmotic pressure,pH,nutrition (food) and gases
Temperature
Bacteria can grow over a wide range of temperature and can survive in the range of -20 to 90oC.
However, for most pathogens 35-37 oC is the optimal temperature.
Cryophiles
temp range -2 to 4 oC
Psychrotrophs
temp range 20 -30 oC
