| Bacteria and other microorganisms |
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Bacteria:
Very small, relatively simple, single called organisms whose genetic material is not enclosed in a special
nuclear membrane for this, Bacteria are called procaryote.
In general; all living cells can be divided in to two groups, procayotes & eucaryotes, based on their
ultrastructure, Plants & animals are entirely composed of eucaryotic cells.
In the microbial world, bacteria are procayotes, other cellular microbes Fungi (Yeast & mold), Protozoans,
and algae are eucaryotes.
Procaryotes and eucaryotes are chemically similar, sense that they both contain nucleic acid, proteins, lipids,
& carbohydrates. The difference between procaryotic & euocaryotic the primary structure of the cell wall,
membranes & organelles.
Bacteria:
Minute microorganism that is member of the procaryotic world, this group includes eubacteria, or true
bacteria, and archaeobacteria.
Eubacteria & archaeobacteria look similar but differ in the chemical composition.
Individual bacteria may form pairs, chains, clusters or other groupings such formations are characteristic of
particular species.
Bacteria enclosed in cell walls that are largely composed of substance called peptidoglycan.
Bacteria generally reproduce by dividing in to two equal daughter cells, this process called binary fission.
Thousand of bacteria differentiated by many factors, including
*Morphology (shape)
*Chemical composition (often detected by staining reactions)
*Nutritional requirements
*Biochemical activities
*Source of energy For nutrition, most bacteria use organic chemicals which in nature can be derived from
other dead organisms or from a living host, some bacteria manufacture their own food by photosynthesis, and
some can derive nutrition from inorganic.
A * Structure of the bacteria
1.External to the cell
2.Cell wall
3.Internal to the cell wall
A 1.External to the cell
a. Glycocalyx
b. Flagella
c. Axial Filaments
d. Pili
A1a. Glycocalyx: Is a viscous (sticky), gelatinous polymer that is external to the cell wall and is composed of
polysaccharide, polypiptide, or both.
When Glycocalyx is firmly attached to the cell wall and organized called capsule (indicated by India ink
method) but if the Glycocalyx unorganized and only loosely attached to the cell wall is called slim layer.
N.B. Capsule is important in contributing to bacteria virulence .
(The degree to which a pathogen causes disease) in certain species.
1.Capsule protects the bacteria from phagocytosis by the cells of the host.
2.Capsule allow the bacterium to attached to various surfaces in order to survive. For this reason bacteria can
live on rocks, plant roots, human teeth and also on other bacteria.
EX.:
*Streptococcus mutans: cause of dental caries
*Klebsiella pnemoniae its capsule protects it self from phagocytosis and so adhere to and colonize to the
Respiratory Tract
3.Can be source of food when the energy source is low.
4.Can protect cells against dehydration.
5.Its viscosity inhibits the movement of the nutrients from the cell
A1b.Flagella:
Flagella: Singular, flagellum, meaning (whip), and long filamentous appendages that propel bacteria.
The flagellum has 3 parts:
1.Filament
2.Flagellin
3.Basal body
The flagella protein serve to identify certain pathogenic bacteria.
A 1 c. Axial Filaments
Bundles of fibrils that arise at the ends of the cell beneath the outer sheath and spiral around the cell and are
cored at one of the end of the spirochete ,have a structure similar to that of flagella.
Spirochetes move by the means of axial filaments, Spirochetes are group of bacteria that have unique
structure and motility.
cause
Exp. of Spirochetes
Teponema pallidum: the causative agent of syphilis
Borrelia burgdorferi: the causative agent of lyme disease
A 1 d. Fimbriae & Pili
Many Gram negative bacteria contain hair like appendages that are shorter, straighter, and thinner than
flagella and are used for attachment rather than for motility. These structure consist of a protein called pilin
arranged helically around a central core and are divided into two types, fimbriae and pili with very different
function
Fimbriae
Occur at the poles of the bacteria cell or they can be evenly distributed over the entire surface of the cell.
They can number anywhere from a few to several hundred per cell.
Pili
Longer than fimbriae and are number only one or two per cell. Pili function to join bacterial cell prior to the
transfer of DNA from one cell to another. They are some times called sex pili
Very small, relatively simple, single called organisms whose genetic material is not enclosed in a special
nuclear membrane for this, Bacteria are called procaryote.
In general; all living cells can be divided in to two groups, procayotes & eucaryotes, based on their
ultrastructure, Plants & animals are entirely composed of eucaryotic cells.
In the microbial world, bacteria are procayotes, other cellular microbes Fungi (Yeast & mold), Protozoans,
and algae are eucaryotes.
Procaryotes and eucaryotes are chemically similar, sense that they both contain nucleic acid, proteins, lipids,
& carbohydrates. The difference between procaryotic & euocaryotic the primary structure of the cell wall,
membranes & organelles.
Bacteria:
Minute microorganism that is member of the procaryotic world, this group includes eubacteria, or true
bacteria, and archaeobacteria.
Eubacteria & archaeobacteria look similar but differ in the chemical composition.
Individual bacteria may form pairs, chains, clusters or other groupings such formations are characteristic of
particular species.
Bacteria enclosed in cell walls that are largely composed of substance called peptidoglycan.
Bacteria generally reproduce by dividing in to two equal daughter cells, this process called binary fission.
Thousand of bacteria differentiated by many factors, including
*Morphology (shape)
*Chemical composition (often detected by staining reactions)
*Nutritional requirements
*Biochemical activities
*Source of energy For nutrition, most bacteria use organic chemicals which in nature can be derived from
other dead organisms or from a living host, some bacteria manufacture their own food by photosynthesis, and
some can derive nutrition from inorganic.
A * Structure of the bacteria
1.External to the cell
2.Cell wall
3.Internal to the cell wall
A 1.External to the cell
a. Glycocalyx
b. Flagella
c. Axial Filaments
d. Pili
A1a. Glycocalyx: Is a viscous (sticky), gelatinous polymer that is external to the cell wall and is composed of
polysaccharide, polypiptide, or both.
When Glycocalyx is firmly attached to the cell wall and organized called capsule (indicated by India ink
method) but if the Glycocalyx unorganized and only loosely attached to the cell wall is called slim layer.
N.B. Capsule is important in contributing to bacteria virulence .
(The degree to which a pathogen causes disease) in certain species.
1.Capsule protects the bacteria from phagocytosis by the cells of the host.
2.Capsule allow the bacterium to attached to various surfaces in order to survive. For this reason bacteria can
live on rocks, plant roots, human teeth and also on other bacteria.
EX.:
*Streptococcus mutans: cause of dental caries
*Klebsiella pnemoniae its capsule protects it self from phagocytosis and so adhere to and colonize to the
Respiratory Tract
3.Can be source of food when the energy source is low.
4.Can protect cells against dehydration.
5.Its viscosity inhibits the movement of the nutrients from the cell
A1b.Flagella:
Flagella: Singular, flagellum, meaning (whip), and long filamentous appendages that propel bacteria.
The flagellum has 3 parts:
1.Filament
2.Flagellin
3.Basal body
The flagella protein serve to identify certain pathogenic bacteria.
A 1 c. Axial Filaments
Bundles of fibrils that arise at the ends of the cell beneath the outer sheath and spiral around the cell and are
cored at one of the end of the spirochete ,have a structure similar to that of flagella.
Spirochetes move by the means of axial filaments, Spirochetes are group of bacteria that have unique
structure and motility.
cause
Exp. of Spirochetes
Teponema pallidum: the causative agent of syphilis
Borrelia burgdorferi: the causative agent of lyme disease
A 1 d. Fimbriae & Pili
Many Gram negative bacteria contain hair like appendages that are shorter, straighter, and thinner than
flagella and are used for attachment rather than for motility. These structure consist of a protein called pilin
arranged helically around a central core and are divided into two types, fimbriae and pili with very different
function
Fimbriae
Occur at the poles of the bacteria cell or they can be evenly distributed over the entire surface of the cell.
They can number anywhere from a few to several hundred per cell.
Pili
Longer than fimbriae and are number only one or two per cell. Pili function to join bacterial cell prior to the
transfer of DNA from one cell to another. They are some times called sex pili