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BACTERIA

CLS 311: Basic MicrobiologyMrs. Amany Ahmed Niazy

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Bacteria are the smallest and most versatile

independently living cells known.

+Microorganism

s

Acellular

Cellular

Prokaryotes Eukaryotes

Archaea

Bacteria

Viruses

Protozoae

Fungi .

+History

Anton van Leeuwenhoek (1632-1723):

He is the father of microbiology.

Known for his invention of the single-lens microscope.

Bacteria were first observed by him in 1676.

HistoryLouis Pasteur (1822-1895).

discoveries helped to formulate “germ theory of disease” .

Invention of pasteurization.

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Robert Koch (1843-1910):

German physician.

He confirmed the germ theory of disease.

He became famous for isolating Bacillus anthracis, the Tuberculosis bacillus and Vibrio cholerae and for his development of Koch's postulates.

He won a Nobel Prize on 1905.

Monument to Robert Koch in Berlin

Prokaryotes

There are two major types of prokaryotes:

1. Bacteria.

2. Archaea (also called archaebacteria)

are often found in extreme environments (Oxygen-free environments

concentrated salt-water hot, acidic water), and while they are clearly

prokaryotic, they have evolved separately from bacteria.

Prokaryotic cells possess simpler

structures than eukaryotic cells , since

they do not have a nucleus or many

cytoplasmic organelles.

+Bacteriology

It is a branch of microbiology that is concerned with bacteria

Bacteria – single celled organism that multiply by binary fission Larger and more complex than viruses Viable under light microscope Prokaryotic, has both DNA and RNA

Introduction

Bacteria (plural), Bacterium (singular).

Bacteriology The study of bacteria.

Bacteria are unicellular microscopic prokaryotes.

Bacteria are ubiquitous in every habitat on Earth,

growing in soil, acidic hot springs, radioactive waste,

water, and deep in the Earth's crust, as well as in organic

matter and the live bodies of plants and animals.

Bacteria are vital in recycling nutrients such as the

fixation of nitrogen from the atmosphere and

decomposition of dead organic materials.

Morphological features of bacteria

SizeUnit of microbial measurement is the micrometer (m), formerly micron () which is equal to: 1m = 1/1000 of a millimeter (mm)

Average size of the bacteria generally varies from 0.5 – 2m in diameter and 2 – 8m in length.

+Fundamental Shapes

Bacilli (bacillus, singular) – rod shaped organisms

Cocci (coccus, singular) – spherical or round organisms

Spirilla (spirillum, singular) – spiralled or comma-shaped organisms

Bacilli

Cocci

SPIRILLUM

+Bacterial Arrangements

Two factors that affect bacterial arrangements:

Plane of division

Position taken after cell division

Pairs: – diplococci (e.g. N.gonorrheae)

DIPLOCOCCI

Chains – streptococci,

STREPTOCOCCI

Grapelike clusters – staphylococci

STAPHYLOCOCCI

Groups of four – tetrads (e.g., Peptococcus)

TETRADS

Packets of eight – cuboidal (e.g., Sarcinae)

PACKETS OF EIGHT

Palisades (slipping)

– organisms tend to place themselves side by side

(e.g., Corynebacterium)

PALISADES

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CLASSIFICATION and TAXONOMY

+What is Taxonomy

Greek words “taxes” – arrangement, “nomos” – law

The science of classification.

The branch of biology concerned with the classification of organisms into groups based on similarities of structure, origin, etc.

+Classification of Organisms

Based on the is based on similarities and differences in genotypes and phenotypes

Microbiologist traditionally emphasize placement and naming of bacterial species into three categories Family (similar to Human clans) Genus (equivalent to human last name) Species (equivalent to human 1st name)

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+Nomenclature

Nomenclature provides naming assignments for each organism.

Assignment of names for purposes of communication and identification

Use a binomial systems of nomenclature

Standard rules for bacterial names: The name of the family is CAPITALIZED

and has an aceae ending (ex:Enterobacteriaceae)

Binomial nomenclature Genus & species

Escherichia coliGenus name is always capitalized Species name is never capitalized coliBoth names are always either italicized or underlined Abbreviation: E. coli

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The plural of genus is genera and there are many genera in the family Enterobacteriaceae

Ex: Famliy: Enterobacteriaceae Genus: Escherichia Species: coli

The International Committee on Systematic Bacteriology

(ICSB) maintains international rules for the naming of bacteria

and taxonomic categories and for the ranking of them in the

International Code of Nomenclature of Bacteria.

Kingdom Bacteria

Phylum Proteobacteria

Class Gamma Proteobacteria

Order Enterobacteriales

Family Enterobacteriaceae

Genus Escherichia

Species Escherichia coli

e.g. Escherichia coli

+Identification

Application of classification & nomenclature to assign proper name to unknown organism and

place it in its proper position within classification system.