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What is microbiology. Study of Micro-organisms: Organisms that EXIST as Single Cells or cell clusters and must be viewed individually with the aid of a Microscope. 1. EXIST (Webster definition)To continue to be, have life; live. HALLMARKS OF LIFE

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What is microbiology

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What is microbiology

Study of Micro-organisms: Organisms that EXIST as Single

Cells or cell clusters and must be viewed individually with the

aid of a Microscope

1. EXIST (Webster definition)To continue to be, have life; live


  • METABOLISM (nutrient uptake, biomass, waste output)

  • DIFFERENTIATION (Bacillus spp. Caulobacter)

  • REPRODUCTION (binary fission)

  • COMMUNICATION (Pseudomonas aeruginosa)

  • EVOLUTION (antibiotic resistance, pathogens)


Take in nutrients from the environment

glucose, lactose, other sugars, fats=lipids, proteins,

toxic wastes, oils and petrol

Assimilate the nutrients into BIOMASS

DNA, proteins, carbohydrates and

complex carbohydrates, lipids

Release waste products into the environment

gases, alcohols, acids and organic compounds

Differentiation— to form distinctstructures

K.C. Keiler

M. Dworkin

Caulobacter spp. Vegetative cells versus stalk cells

Differentiation— to form distinctstructures

T.J. Deveridge

M. Dworkin

Bacillus spp. endospore forming cells

Anabaena spp. Cyanobacteria forming heterocysts


J. Pitocchelli

E. Hettema

To generate progeny of ones same type

A bacterium duplicates its DNA and forms a daughter cell via binary fission

Yeast duplicates its DNA and forms a daughter cell via budding, or mates with

another yeast cell and produces haploid progeny.

Communicationinteraction withother cells—response to other cellsVibrio fischeri and Lantern fish


Kolter and Losick

CommunicationBiofilms andHealth




To change ones genetic make up (DNA sequence) to

adapt to ones environment

Bacteria can take up DNA from the environment or other cells via

Transformation—uptake of naked DNA

Transduction—phage (bacterial specific virus) mediated

uptake of DNA

Conjugation—uptake of DNA that requires the interaction

of two bacteria

Antibiotic resistance, bacterial pathogenesis

What is microbiology

Study of Micro-organisms: Organisms that EXIST as Single

Cells or cell clusters and must be viewed individually with the

aid of a Microscope

2.KEYWORDsingleCELLS(OR cell clusters)



  • CELL MEMBRANE –barrier that separates the inside of the cell from the outside

  • NUCLEUS OR NUCLEIOD – location of genetic information (DNA)

  • CYTOPLASM –location of the machinery for cell growth and function

  • MACROMOLECULES – proteins, nucleic acids, lipids, polysaccharides

3.KEYWORDexist asSINGLEcells(OR cell clusters)

We are multicellular creatures—made up of manycells

What makes one of our cells different from a microbial cell??

A single microbial cell can have an independent existence—our

specialized cells need to interact with other cells in order to carry

out their cellular functions for the good of the entire organism.

What organisms are considered to be microbial cells and studied in microbiology





  • Viruses(although not a cellular entity but an

  • intracellular pathogen)

  • Prions (a biochemical anomaly—misfolded proteins)

  • Helminths Worms (multicellular)


The study of phylogenetic relationships between organisms

(The sorting of all living things based on their related or differentiating features)

KINDOM the highest level in classification

PHYLUM related classes

CLASS related orders

ORDER related families

FAMILY related genera

GENUS closely related species

SPECIES organisms sharing a set of biological traits and

reproducing only with their exact kind

Further classifications especially with bacteria:

Strain—organisms within a species varying in a given quality

Type—organisms within a species varying immunologically

Taxonomy::relatively easy to classify animals and plants based on their behaviour and appearance—old school

Taxonomy::initially not easy to classify microorganisms based on their behaviour and appearance

Advancements in DNA amplification and DNA sequencing has greatly helped

The phylogenetic relationships between microorganisms can be determined by sequencing the 16S and 18S ribosomal RNA of the organisms in question

(ribosomal RNA—structural RNA of the ribosome that plays a role in protein synthesis)

Phylogenetic classification of micro-organisms (new school)








Universal Ancestor

Phylogenetic classification of micro-organisms

EUBACTERIAmost abundant of the bacteria

found in soil, water and animal digestive tracts

ARCHAEACTERIA live in extreme conditions (temperature, pH etc) mostly anaerobic (unable to live in the presence of oxygen)

EUKARYOTESalgae: live in soil and water, contains chlorophyll for photosynthesis, has a cell wall

fungi: yeast, molds. Lack chlorophyll and obtains energy from organic compounds in soil and water, has a cell wall

protozoa: colorless, lacks a cell wall, ingests other organisms or organic particles

Major Differences between prokaryotic and eukaryotic micro-organisms

  • Prokaryotes

  • 1. Nonmembrane bound

  • nucleiod region

  • DNA-one circular molecule

  • one chromosome

  • Haploid-One copy of a gene

  • Plasma membrane does not

  • contain sterols

  • Reproduction—simple binary

  • fission

  • Eukaryotes

  • 1. Membrane bound nucleus

  • containing DNA

  • DNA-linear molecules arranged

  • to form several chromosomes

  • Diploid-Two copies of a gene

  • Plasma membrane contains

  • sterols

  • Reproduction—meiosis and

  • mitosis

  • Presence of membrane bound

  • organelles such as chloroplasts

  • and mitochondria

Why study Microbiology ??

Microbiology as a BASIC Science

Bacteria and yeast are useful in studying molecular biology, biochemistry and genetics

--reproduce rapidly

--are genetically (DNA) and biochemically more simple than higher order organisms

--working with bacteria and yeast for understanding life processes has no ethical ramifications

Microbiology as an APPLIED Science

Medicine—Vaccine development, production of antibiotics,

production of important biological enzymes (insulin)

Industry—Production of beer, wine, cheeses and yogurt

Agriculture—maintenance of soil fertility/digestion in cattle

Ecology—Bioremediation—microorganisms that degrade

toxic waste materials

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