Lack a nucleus DNA is naked a single loop not bound in a chromosome May contain plasmids small circular fragments of DNA Have ribosomes but no other organelles DNA present as a long circular molecule ID: 751175
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Slide1
BACTERIA Slide2
Bacteria
Cells are prokaryotic and amongst the smallest known cells ( length 0.5-20 µm ).
Lack a nucleus
DNA is naked, a single loop not bound in a chromosome
May contain plasmids (small circular fragments of DNA)
Have ribosomes, but no other organelles.
DNA present as a long circular molecule.Slide3
Structure of a Bacteria Slide4
Classification
All bacteria are prokaryotes, which can be placed in one of two kingdoms:
Archaebacteria: “Ancient Bacteria”
Archaebacteria “True Bacteria”Slide5
Archaebacteria
“Archae” means primitive or early
Oldest organisms on the plant ~ 3 billion yrs old
Live in extreme conditions: Environments in which no other organisms can survive Slide6
Environments of Archaebacteria
These bacteria are characterized as living in extreme conditions that have:
High temperatures (Thermophiles)
Low temperatures (Psychrophiles)
High Salt concentrations (Halophiles)
High acidity
Environments with no oxygen (
anerobic
)Slide7
Archaebacteria
Thermophilic bacteria thrive in volcanic vents
Halophilic bacteria thrive in salty lakes Slide8
Eubacteria
All other bacteria.
Strong cell walls and less complicated genetic makeup.
Live in many habitats
Most common form of life on earth
Can be bad (pathogens) or good (digestion)
Organisms: Bacteria
, Cyanobacteria Slide9
How to Classify Bacteria
Shape
Cell
walls
How they move
How they obtain Energy Slide10
Cell Shape
One way that bacteria can be identified is by their shape:
Lactobacilli:
rod-shaped
Spirochaeta:
spiral
Enterococci:
spherical
Rod-shaped, called Bacilli
Spiral, called Spirilla or Spirochetes
Spherical
Slide11
Coccus
Spherical shaped bacteria are called Cocci
Single cells - monococci
Pairs - diplococci
Chains - streptococciSlide12
Bacillus
Rod shaped Bacteria are called Bacilli
Exists as: Single Cells
In pairs (diplobacilli)
In chains (streptobacilli).Slide13
Spirilla
Spiral shaped bacteria are called Spirilla
Spirillum (Singular)
Plural is spirilli.
Exist only as single cells.Slide14
Cell Wall
The chemical nature of a cell wall can be studied by a method known as Gram
Staining
Hans Christian Gram: inventor of Gram StainingSlide15
Gram Staining
Gram stains contain of two dyes
Crystal Violet (Purple)
Safranine (Red)
Gram-positive bacteria: cells with only 1 thick layer of carbohydrate and protein molecules took up the crystal violet dye.
Gram-negative bacteria: cells wall contains a second layer of lip and carbohydrate took up the crystal violet dye.Slide16
Gram positive:
Appears
violet
after Gram’s stain
b)
Gram negative:
Appears
red
after Gram’s
stain
GRAM STAIN
It
is the most important differential stain used in bacteriology because
it
classified bacteria into two major groups:Slide17
Bacterial Movement
Some bacteria propel themselves by the means of 1 or more whip-like structures called a flagella
Some bacteria produce a thick layer of slime to glide about
Others remain stationary
Bacteria can be identified by studying how them move:Slide18
How bacteria obtain Energy
Autotrophs:
Organisms that make their own energy
Phototrophic Autotrophs:
Bacteria that get there energy from sunlight
Chemotropic Autotrophs:
Bacteria that obtain their energy from inorganic molecules
Inorganic molecules: Hydrogen sulphide, nitrites, sulphur and iron Slide19
Examples of Autotrophic Bacteria
Phototrophic autotroph: Cyanobacteria
Chemotrophic Autotrophs: Ecoli bacteria Slide20
How Bacteria obtain Energy
HETEROTROPHS:
Energy is obtained from other organisms
Chemotrophic heterotrophs:
obtain energy by dissolving and absorbing organic material
Phototrophic heterotrophs :
obtain sunlight for energy, but need organic compound for nutrition.Slide21
Examples of Heterotrophic Bacteria
Chemotrophic heterotroph: SalmonellaSlide22
Bacterial Respiration and Fermentation
Bacteria need a constant supply of energy to perform their life activities
Energy is supplied by the process of:
Respiration: A process that involves oxygen and the breakdown of food molecules to release energy
Fermentation: the process that enables cells to carry out energy production in the absence of oxygenSlide23
Bacterial Respiration
Bacteria can be classified into three categories based on their need for oxygen
1. Obligate aerobe: Must have O
2
to live
2. Obligate anaerobes: Must live in O
2
free environment
3. Facultative anaerobes: Can live with or without O
2Slide24
RECAP QUESTIONS
How would this bacteria be classified according
to shape?
Is this bacteria a Gram-positive or Gram-negative bacteria?