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What are bacteria?
Bacteria are single celled organisms that lack a nucleus, and multiply by cell division.Are they eukaryotic or prokaryotic cells?
Bacteria can be found virtually everywhere!They are found in the air, soil, water, in and on plants and animals including humans.Did you know?A single teaspoon of topsoil contains approximately 1 billion bacterial cells.
The human mouth is home to more than 500 different species of bacteria.
Humans are colonized by many different species of bacteria.
Methods of transmission:
Saliva, aerosolsBlood
Skin contactGenital secretionsFaecal-oral routeVectors such as
mosquitoes
Sites of contamination:
EyesNose and throat
MouthAirways and lungs
SkinStomach and intestines
Urinary tractGenital tract
Question:
How many bacteria are present per cm2 on the
human skin?Answer:
An average of 100,000 bacteria!
Bacteria have:
• Ribosomes
• DNA
• Plasma membrane
• Cell wall
• Capsule
• Flagellum
• Pili
Bacteria possess a very simple structure:
BUT…don’t be fooled! They are an amazingly complex and
fascinating group of organisms.
Bacterial Capsule Stain!!!- Capsules enhance
the ability of bacteria to cause disease
Bacteria come in a wide range of shapes, sizes and colours!
• Three main shapes are–1. Bacilli-rod shaped–2. Cocci-sphere shaped–3. Spirilla-corkscrew shaped
• Two major configurations are:–Strep- chain–Staph- cluster
Examples of various species’ shapes, sizes and colors!
Bacillus Bordetella Clostridium Escherichia
Spirulina StaphylococcusStreptococcus Salmonella
Gram Stain from a clinical specimen
Human White blood
cell
Bacteria staining as gram positive rods
How do we visualize bacteria?Bacterial cells can only be seen using a
microscope. Various staining techniques may be used in order to aid this.
How bacteria get ENERGY?
• Most are HETEROTROPHS – Chemoheterotrophs- use organic molecules
for a Carbon and energy source– Humans are chemoheterotrophs too and if we do
not handle food carefully, bacteria will get to OUR food before we do.
– Photoheterotrophs- use organic molecules for Carbon source and sunlight for energy
How bacteria get ENERGY?
• Some are AUTOTROPHS–Photoautotroph- use sunlight to
convert CO2 and H2O to Carbon compounds and O2
–Chemoautotroph- make Carbon compounds from CO2, but don’t use sunlight, they use energy from chemical reactions
How do they use Oxygen?
• Obligate aerobes- require O2 (respiration)
• Obligate anaerobes- must live without O2 (fermentation)
• Facultative anaerobes- survive with or without O2 (switch between respiration and fermentation)
Reproduction
• Binary fission- asexual reproduction happens when a bacterium has grown so that it has nearly doubled in size, it replicates its DNA and it divides in half producing two identical daughter cells.
1 bacterium1 bacteriumcan becomecan become1/2 million in1/2 million in6-7 hours6-7 hours
BinaryFission
Based on Based on Harvard Medical Harvard Medical School Family Health GuideSchool Family Health Guide
Reproduction
• Conjugation- Exchanging genetic information in which a hollow bridge forms between two bacteria cells and genes are passed. This increases genetic diversity.
Do all bacteria cause disease?
Answer = No
Only a subset of the thousands of species of bacteria are capable of causing disease and then only in certain circumstances.
Bacteria is VITAL
For……
1.) Decomposing
2.) Converting nitrogen gas into a form plants can use known as Nitrogen Fixation.
ALSO………..
Bacteria is VITAL
• To HUMANS–Health
• Skin and intestines
–Everyday use• Industry• Food• Clean up waste• Research
Summary
• What is bacteria?
• Does all bacteria look the same?
• How can we actually “see” bacteria?
• What are the two ways bacteria consumes energy?
• How does bacteria reproduce?
• How is bacteria vital to us?
Diphtheria
Diphtheria
Streptococcus
Staphylococcus