Bacteria

Kingdom bacteria belongs to : Monera

What are the main features of members of kingdom Monera

  1. Prokaryotic

  2. Unicellular : exists as one single cell

  3. Reproduction is asexual

All bacteria have the following features:

  • DNA - code for protein

  • Cell membrane :

    • Semi permeable

    • structure and support

  • Cell wall : keeps cell turgid and prevents cell bursting

  • Cytoplasm : Suspends cell parts

  • Make protein

Some bacteria also have the following features:

Capsule : protection

Plasmid loop : Extra DNA has a role in antibiotic resistance

Flagellum : Help bacteria Swim

Name one way that scientists can classify bacteria : on shape

Bacterial shapes

  1. Spherical

  2. Rods

  3. Spiral

Reproduction in bacteria

What name is given to the way by which bacteria reproduce? : Binary fission

Describe how binary fission occurs in bacteria

  1. DNA replication occurs in parent cell

  2. cell elongates

  3. cell splits, forming two identical daughter cells

Endospores

endospores : dormant tough walled structures that can form in some bacteria during adverse conditions to survive

adverse conditions : unfavorable conditions bacteria die in

Endospore formation in bacteria

  1. RNA replication occurs

  2. adverse conditions an endospore forms

  3. remains dormant

  4. conditions become suitable a new cell forms again

Nutrition in bacteria

  1. Heterotrophic

    • take in food from other organisms, do not make their own food.

      • Saprophytes - feed on dead organic matter (bacteria of decay)

      • Parasites - feed on live host, causing harm (Streptococcus)

  2. Autotrophic

    • Make own food using energy

      • Photosynthetic - use light make own food (Purple sulfur bacteria)

      • Chemosynthetic - use chemical reactions to make own food (Nitrifying bacteria)

Factors affecting bacteria growth - assuming they have food source

  1. temperature

    • low temperatures - enzyme action is low

    • high temperatures - enzymes denatured

    • most bacteria grow well at temps between 20 and 30 degrees (optimum temperature)

  2. pH

    • bacteria placed in an unsuitable pH will have its enzymes denatured

    • most bacteria grow well at pH close to 7

  3. Oxygen concentration

    • aerobic bacteria require oxygen for respiration

    • anaerobic bacteria does no require oxygen for respiration

      • Anaerobic bacteria :

        • obligate anaerobes - cannot survive in oxygen

        • facultative anaerobes - can survive with or without oxygen

  4. Concentration of growing medium

    • Salty/Sugary solution :

      • water leave cell by osmosis

      • plasmolyzed die

    • Fresh water solution :

      • water enter the cell by osmosis

      • cell wall prevent from bursting

      • cell turgid

  5. Pressure

    • High pressures can destroy cell walls

Growth curve of bacteria

  • The growth curve for a typical bacteria culture is as follows:

Explaining the growth curve

A) Lag phase

  • Little increase

  • adapting to environment

B) Log phase

  • Rapid increase

    • due to plenty of food, water, space, oxygen. Not much waste products or competition

C) Stationary phase

  • No increase or decrease

    death rate = reproductive rate

  • due to:

    • Lack of food and water, space, oxygen

    • Build up of waste and competition

D) Decline phase

  • Numbers decrease - death rate greater than reproductive rate

  • Due to:

    • lack of food, water, space, oxygen

    • Build up waste + competition

E) Death or survival phrase

  • Most die, some survive as endospores

Antibiotics and Resistance

What are anti biotics? : produced by micro organisms that kill other micro organisms

example : penicillin

Why will antibiotics not be prescribed to a person suffering from cold/flu/covid like symptoms?

  • Antibiotics have no effect on viruses

  • cold/flu/covid caused by viruses

What are anti-biotic resistant bacteria?

  • bacteria not affected by antibiotics

What feature present in a bacteria cell plays a role in antibiotic resistance?

  • plasmids

Overuse of antibiotics result in the increased growth of anti-biotic resistant bacteria. Why?

  • mutations, anti-biotic resistant bacteria

  • widespread use of antibiotics “normal” bacteria are killed quickly

  • anti biotic resistant bacteria, no competition and reproduce rapidly and their numbers increase

Using your knowledge of antibiotics and bacteria, suggest why a person is more likely to pick up an infection in hospital than at home.

  • numbers thrive where many antibiotics are used. only bacteria can survive

Food processing

  1. Batch Culture

    • fixed amount of nutrient and bacteria and left for time before product removed

    • lag log stationary and decline phase

      • Adv - easy to maintain

      • Dis - needs to be purified

  2. Continuous flow

    • New nutrient constantly added and product constantly removed

    • log phase

      • Adv - product purity is higher

      • Dis - difficult to maintain

Economic importance of bacteria

Benefits

  • Bio processing (dairy)

  • Genetic engineering

Disadvantages

  • cause disease - pathogens (Streptococcus, tetanus, syphilis

  • cause food to decay