Introduction to Microbiology

Maria Simatupang,drDept. of MicrobiologyMedical FacultyUSU

Microbiology definedThe study of organisms, where the individual cells of the 'microbe' can't be seen by the unaided human eye'

That is, we need to use specialized detection systems-usually optical instruments termed microscopes.There are 2 main type main types of microscopes in use:Bright field microscope resolution about 0.2mElectron microscope: resolution about 100 times greater

What is microbiology?BacteriologyVirologyMycologyImmunologyGenetics

Comparison of medicaly important organismsCharacteristic Viruses Bacteria Fungi Protozoa &HelminthCells No Yes Yes YesDiameter(m) 0.02-0.2 1-5 3-10 15-25 (yeast) (tropozoites)Nucl.acid either DNA both DNA both DNA both DNA or RNA or RNA or RNA or RNA Type of nucleus none Prokaryotic Eukaryotic EukaryoticRibosomes- +++ Mitochondria--++Outer surce protein capsid peptidoglican chitin flexible & lipoprotein envelope membraneMotility nonesome none noneMethod of not binary fission binary fission budding or mitosisReplication mitosis

The microbial world 2 divisions Procaryotes& EucaryotesProcaryotes (refers mainly to the bacteria)No nucleusGenerally circular DNA genome+/- cell wallCan have extrasomal DNADNA without intronsHaploid (chromosome)Binary division

The 2nd microbial divisionEucaryotes (includes parasites and fungi)Have nucleusOther membrane organellesDiploid chromosomesMitotic & meiotic divisionHave introns and exons

In clinical microbiology we have interest in bothBacteria (procaryotic)Eg Staph sp, Strep sp, E.coli, Mycoplasma spFungi (eucaryotic)Candida sp (single celled yeast), Aspergillus sp (multicelled)Parasites (eucaryotic)Giardia lamblia, Plasmodium sp (malaria)Viruses HIV, HBV, HBC, Rubella, Herpes (EBV, VZ, HSV)

A little HistoryMain events & peopleBefore about 1650 philosophers believed in SPONTANEOUS GENERATION Significant discoveries altered this thinking.

Some of the key players were:

ANTON van LEEUWENHOEK, 1674Mid 17th Century probably 1st to observe bacteria under magnification

Although Robert Hooke first to observe microbes through magnification- Its thought he saw protozoaie larger cells such as amoebae

Edward Jenner 1796- First successful vaccination.Relationship of cowpox to smallpoxSmallpox (virus)30-40% mortalityViremia followed by deathLast naturally occurring case in Africa, 1976. Role of WHO in smallpox eradicationPossible because humans are the only smallpox host.

LOUIS PASTEUR:Demonstrated by the use of sterile media that microbes were in fact present in air, And that air in does not create microbes Used broths in flasks and S funneled microbial trap experimentsFermentationPasteurization

Joseph LISTER (1860)Adopted the use of 'aseptic' techniques which lead to its general adoption

ROBERT KOCH (1876)Proved beyond doubt that specific organisms were the cause of specific infectious diseases.Experiments with the very lethal disease (especially of cattle) anthraxKoch and wife1905-Nobel Prize

KOCHS POSTULATES1. The same 'pathogen' must be present in every case of the disease2. The pathogen must be isolated from the diseased host and grown in pure culture3. The pathogen when inoculated into a susceptible uninfected host causes the disease4. The pathogen must be re-isolated in pure culture from the inoculated animal

Griffith 1928 Experiment to determine which part of a pneumococcus bacteria caused the disease.1944 Genetic material is DNA, not the capsule, not the cytoplasm. Provided the groundwork for Avery and McLeods definitive work, as well as for Watson and Crick (1953) DNA StructureFleming 1929 Penicillin (beta lactam ring in outer layer of a bacteria is inhibited, making cell wall synthesis impossible)

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