Monera

Monera Unicellular Flagellum Plasmid

Capsule Binary Fission

Endospore Autotrophic

Heterotrophic Saprophytes

Parasites KEYWORDS Photosynthetic

Chemosynthetic Obligate anaerobes

Facultative anaerobes Pathogens

Antibiotics Batch culture Continuous culture

Structure of a bacterial cell

Monera (bacteria)

• Bacteria are found everywhere on the planet.

• Some can even withstand high temperature and pressures.

Note: a pathogen is a micro-organism that causes a disease.

Facts on bacteria

• Single celled organisms (unicellular)

• Very small

• Mesosomes are used for respiration in the bacterial cell.

• Cell walls prevent the cell from swelling and bursting.

Facts on bacteria

• Capsule (slime layer) is used to protect bacteria.

• Contain plasmids (genes) that can be responsible for antibiotic resistance.

• Flagella allow the bacteria to move around.

NOTE:

Monera are prokaryotic (they don’t have a nucleus or membrane enclosed organelles).

Types of bacteria

Three types of bacteria:

1) Round bacteria

2) Rod bacteria

3) Spiral bacteria

Round bacteria (Coccus)

Pneumonia

Sore throat

Food poisoning

Boils caused by round bacteria

Rod Bacteria (Bacillus)

Tuberculosis

Tetanus

Video on Tetanus

• Tetanus - YouTube

Botulism

Clostridium botulinum and Botulism - YouTube

Spiral bacteria (Spirillum)

Syphilis

Cholera

How bacteria reproduce?

Bacteria reproduce by a process called binary fission (asexual).

• DNA replicates (there are two identical strands of DNA)

• The bacteria split into two identical sized cells.

• Bacteria can divide every 20 minutes.

Binary fission

Binary Fission

Mutations in bacteria • Bacteria can evolve very fast due to the speed in which

mutations can spread from the rapid speed from reproduction.

• This results in the resistance to new antibiotics.

Endospores

• Some bacteria can withstand harsh and unfavourable conditions (lack of food, high temperature) by producing endospores.

• A tough walled endospore forms around the bacterial chromosome which can remain dormant for a long time.

• When conditions become suitable, endospore absorbs water and the tough wall breaks down.

Growth of an Endospore

Endospore

DNA

Nutrition of bacteria

Two types of Nutrition:

1) Autotrophic: organisms that make their own food.

2) Heterotrophic: organisms that take in food from other organisms.

Autotrophic bacteria

Types of autotrophic bacteria:

1) Photosynthetic bacteria: have chlorophyll and use light to make their own food

(e.g Purple sulfur bacteria)

2) Chemosynthetic bacteria: make food using energy from chemical reactions . (e.g Nitrifying bacteria)

Heterotrophic bacteria

Types of heterotrophic bacteria:

1) Saprophytes: take in food from dead organic matter (e.g bacteria of decay)

2) Parasites: take in food from a live host and cause harm (e.g tetanus)

Bacterial Nutrition

Heterotrophic Autotrophic

Saprophytic Parasitic Photosynthetic Chemosynthetic

Factors affecting growth

1) Temperature

2) Oxygen concentration

3) pH

4) External solute concentration

5) Pressure

NOTE: bacterial depend on bacterial enzymes for many functions.

Temperature affecting bacteria

• Bacteria normally grow well between 20 – 30oC

• Lower temperatures slow down the rate of bacterial growth.

Oxygen Concentration and bacteria

Aerobic bacteria require oxygen for respiration.

• Low oxygen levels can slow down bacterial growth.

Obligate anaerobes bacteria can only respire in the absence of oxygen

(e.g tetanus)

• Facultative anaerobes: can respire with or without oxygen.

Example: E. coli.

pH and bacteria

• If bacteria is present in unsuitable pH values, the bacteria’s enzyme will become denatured.

• This slows down the growth of the bacteria.

NOTE: Helicobacter bacteria are found in half the irish population in the stomach (pH2) which cause stomach ulcers

External solute concentration and bacteria

• Water can move in and out of a bacterial cell depending on the external solute concentration the bacterial cell is in.

• They gain or lose water due to osmosis.

Allows for food preservation by salting food.

Pressure

• The growth of most bacteria is inhibited by high pressure.

NOTE: some bacteria can survive high pressure conditions such

as in deep sea vents.

Benefits of bacteria

• Bacteria convert milk to products such as cheese, yoghurt.

• Bacteria are used to make antibiotics, vinegar and pickles.

• Genetically modified bacteria are used to make insulin, drugs and enzymes, vitamins, alcohols.

Disadvantages of bacteria

• Bacteria cause plant, human and animal diseases.

• Examples: whooping cough, meningitis and tuberculosis, tooth decay.

• Pathogens are bacteria that cause diseases.

Disadvantages of bacteria

• Bacteria cause food decay such as turning milk sour.

Growth curve of bacteria

Growth Curve of bacteria

Lag Phase (A): Bacteria are adapting themselves to their new environment. Little or no increase in the bacterial population.

Log Phase (B) : Bacteria are reproducing at their maximum rate. This is due to ideal conditions (plenty of food, moisture, oxygen)

Growth Curve of Bacteria

Stationary Phase (C) :

• No increase in bacterial numbers.

• Birth rate equals the date rate.

• This is due to lack of food, oxygen, space, and build up of toxic wastes.

Growth Curve of Bacteria

Decline Phase (D) : Bacterial numbers fall due to death rate being higher than birth rate (lack of oxygen, space, food)/

Death or Survival Phase (E) : Not all bacteria die, some can

remain alive by producing spores.

Logarithmic growth of bacteria - YouTube

Food Processing

• Bacteria are involved in bioprocessing methods to produce different foods.

Examples: Yoghurts, cheeses, amino acids, vitamins and alcohol.

There are two methods of bioprocessing:

1) Batch culture

2) Continuous Flow culture

Food processing:

• Bioprocessing: is a technique in which micro-organisms, living cells or their components are used to produce a desired end product.

• A Bioreactor is a receptacle in which bioprocessing is carried out. Called a Fermenter

Bacteria in food - YouTube

Batch Culture

• Fixed amount of sterile nutrient is added to bacteria in bioreactor.

• The product is formed in the log or stationary phase.

Batch Culture

• At the end of process, the bioreactor is emptied.

• Bioreactor is cleaned.

• Many antibiotics are formed in the process.

Batch Culture

Continuous Flow

• Nutrients are continuously added into bioreactor.

• The product is continuously removed also.

• Bacteria are constantly in the log phase, which means product is produced at a fast rate.

Batch Culture

• Fixed amount of nutrient added at start

• Bacteria go through all 5 stages

• Product formed for a short time

Continuous flow Culture

• Nutrients added all the time

• Bacteria maintained in the log phase all the time

• Product formed all the time for a long period

Antibiotics

• Antibiotics are chemicals produced by micro – organisms that stop the growth and kill harmful micro – organisms without damaging human tissue.

• Sir Alexander Fleming found the first antibiotic known as penicillin.

Antibiotics Resistance

Antibiotic Resistance

• Mutations in bacterial genes can allow bacteria to develop antibiotic resistance.

• Antibiotics will then kill bacteria and favour resistant bacteria.

• Bacterial have emerged which are resistant to almost all known antibiotics (multi-resistant). As a result present day antibiotics become ineffective. MRSA is one example.

MSRA and C Difficile

Overuse of antibiotics

What has encouraged bacteria to become anti-biotic resistant?

1) Over use of antibiotics. 2) Failure of some patients to complete a course of antibiotics prescribed to them by a doctor allows the bacteria to survive and re-grow.

Paper 2005 Question 15b

• Draw and label a diagram to show the basic structure of a

typical bacterial cell:

• Other than being prokaryotic, state two ways in which a typical bacterial cell differs from a typical human cell (e.g cheek cell): _________________________________________________

• Describe how some bacteria respond in order to survive when environmental conditions become unfavourable: __________________________________________________

• What is meant when a bacterium is described as being pathogenic: __________________________________________________

• What are antibiotics: Use your knowledge of the Theory of Natural Selection to explain the possible danger involved in the misuse of antibiotics: _____________________________________

Paper 2005 Question 15b

Paper 2006 Question 15b

• Distinguish between photosynthetic and chemosynthetic

bacteria. Give an example of each type: __________________________________________________

• Name two forms of heterotrophic nutrition found in bacteria: __________________________________________________

• Explain what is meant by antibiotic resistance and suggest how it may develop: ____________________________________________________________________________________________________

Paper 2008 Question 15c

• The diagram shows a bacterial growth curve:

• A and B represent the labels on the axes. What does each of them stand for? __________________________________________________

• What term is applied to the part of the curve labelled x ? What is happening during x ? __________________________________________________

• What term is applied to the part of the curve labelled y ? What is happening during y ? __________________________________________________

• Continue the curve to show the next phase. Explain why you have continued the curve in this way: __________________________________________________

• Distinguish between batch and continuous flow food processing using micro-organisms in the food industry: __________________________________________________

Paper 2008 Question 15c

Exam paper 2013, Question 12b: