TOPIC 5: Biologic Attributes of Bacteria

Prokaryotes

Bacteria are what type of organisms?

Binary fission

What asexual process does bacteria use to replicate?

Exponential

What kind of rate is bacteria capable of growing?

Bacterial Growth Curve

Is the graphical representation of the number of cells in a population overtime

1. Lag Phase

2. Log/Exponential Phase

3. Stationary Phase

4. Death Phase

4 Phases of Bacterial Growth Cycle

Lag Phase

• Phase of rejuvenescence of physiologic youth

• Period of active growth during which bacteria prepare for reproduction

• Period of intense metabolic activity involving DNA and enzyme synthesis

• Cell grows in size BUT NO cell division occurs

Log/Exponential Phase

• Phase of bacterial growth in which cellular reproduction is most active

• Cells dividing by binary fission and doubling in numbers at each generation time

Generation Time

The time it takes for the cell to divide (every 20 minutes)

Log/Exponential Phase

In which phase are populations more susceptible to antimicrobial drugs (antibiotics and disinfectants are most effective) that interfere with metabolism and formation of cell structures?

Gram Staining

In the Log/Exponential Phase, what type of staining is preferred because the stain can penetrate faster?

Stationary/Plateau Phase

• Population size is stable

• Available nutrients become depleted and waste products will start to accumulate

• Number of dividing cells will now equal the number of dying cells

• In less favorable conditions, competition for nutrients increases and cells become less metabolically active

Stationary/Plateau Phase

In which phase does spore forming bacteria produce endospores?

Stationary/Plateau Phase

In which phase does pathogenic bacteria begin to generate virulence factors that will help them survive since the condition is harsh already, consequently causing disease?

Chemostat

Special apparatus that can postpone onset of stationary/plateau phase that continually removes wastes along with old medium and some cells

Cultural liquid containing metabolic end products, leftover nutrients, and microorganisms are continually removed at the same rate to keep the culture volume constant

Death Phase

• Phase in which cell death exceeds division

• Nutrients become less available, while waste products are increasing, resulting in the rise of the number of dying cells

• Number of living cells decreases exponentially

Dying cells slice/break open, spilling their contents and making nutrients available to the spore-forming bacteria

What helps spore forming bacteria to survive long enough for spore production during the Death Phase?

Nutrients

What is the Growth Requirement for Bacteria (for energy needs and o build organic molecules and cellular structures)?

1. Passive Transport

2. Active Transport

How are nutrients brought into bacteria?

Passive Transport

Movement of ions and other molecular substance across the cell membrane without the need of energy

Active Transport

Movement of molecules across a membrane from a lower concentration to a higher concentration, requiring ATP or cellular energy

Fastidious

Complex bacteria needing many nutrients

Nonfastidious

Those that can grow easily on simple media without requiring specific or complex nutrients or environmental conditions

1. Carbon

2. Energy

3. Hydrogen

4. Oxygen

5. Nitrogen

6. Phosphorus

7. Sulfur

Nutrients that can help classify bacteria

When bound to hydrogen

When are compounds of carbon classified as organic?

1. Autotrophs

2. Heterotrophs

Two broad groups of organisms based on their carbon source

Autotrophs

• Organisms capable of producing own food form substances available in surroundings by utilizing inorganic carbon (CO2) as their sole source of carbon by using light (photosynthesis) or chemical energy (chemosynthesis)

Heterotrophs

• Catabolize reduced organic molecules (proteins, carbs, amino acids, fatty acids) acquired from other organisms

• Cannot produce or synthesize own food. so rely on other organisms for nutrition

1. Anabolism

2. Intracellular Transport

3. Motility

What are cellular processes that may require energy?

1. Chemotrophs

2. Phototrophs

Organisms categorized according to their energy source

Chemotrophs

• Acquire energy from redox reactions involving inorganic and organic chemicals

• Organisms that get their energy by oxidation or breakdown of CO2 or inorganic chemical compounds by chemical energy

• Reactions may include:

  • Aerobic respiration

  • Anaerobic respiration or fermentation

Aerobic Respiration

Process by which organisms utilize oxygen to turn fuel such as fats and sugars into chemical energy

Anaerobic Respiration or Fermentation

Breaking down of glucose without oxygen

Phototrophs

• Uses lights as their energy source

• Organisms that capture light energy and convert it into chemical energy inside their clel

• Use light energy in order to produce or carry out cellular function

• Main source of energy is sunlight

1. Algae

2. Cyanobacteria

3. Heliobacteria

Examples of Phototrophs

Hydrogen

Is essential for Hydrogen-Bonding and in electron transfer; bacteria use oxidation reduction for electron transfer

1. Organotrophs

2. Lithotrophs

Organisms based on Electron Donors/Hydrogen

Organotrophs

• Organic compounds are used as electron donors

• Acquire electrons from the same organic molecules that provide them carbon and energy

• Use organic molecules, such as sugar and amino acids, as their energy source

• Obtains electrons from the environment

Lithotrophs

• Use inorganic sources of electrons and CO2 as inorganic carbon source

• Acquire electrons or H atoms from inorganic sources:

  • H2

  • NO2-

  • H2S

  • Fe2+

CO2

Inorganic source of carbon used by lithotrophs

1. H₂

2. NO^2-

3. H₂S

4. Fe²⁺

Inorganic sources of electrons used by lithotrophs

1. Obligate Aerobes

2. Obligate Anaerobes

3. Facultative Anaerobes

4. Aerotolerant Anaerobes

5. Microaerophiles

Organisms based on Oxygen Requirement

Obligate Aerobes

(Organisms based on Oxygen Requirement)

• O2 is essential because it serves as the final electron acceptor of electron transport chains (in cellular respiration) which produce most of the ATP in these organisms

• Bacteria cannot survive without oxygen

1. Algae

2. Most fungi

3. Protozoans

4. Many prokaryotes

Examples of Obligate Aerobes

Obligate Anaerobes

(Organisms based on Oxygen Requirement)

• Highly reactive O2 forms are toxic

• Metabolic processes for energy of these organisms are not conducive in the presence of oxygen

• During normal respiration with oxygen, it forms radicals, which are toxic to the organism

1. Singlet Oxygen (O₂)

2. Superoxide (Free) Radical (O₂^-)

3. Peroxide Anion (O₂^2-)

4. Hydroxyl Radical (OH^-)

Toxic Forms of Oxygen

Singlet Oxygen (O₂)

(Toxic Forms of Oxygen)

• Extremely reactive forms of oxygen present in phagocytic cells

• Can cause DNA and protein destruction

Superoxide (Free) Radical (O₂^-₎

(Toxic Forms of Oxygen)

• All organisms growing in atmospheric must produce the enzyme superoxide dismutase to get rid of them, but obligate anaerobes do not possess this enzyme

Peroxide Anion (O₂^2-)

(Toxic Forms of Oxygen)

• Active ingredient of several antimicrobials, like benzoyl peroxide

Hydroxyl Radical (OH-)

(Toxic Forms of Oxygen)

• Toxic to certain bacteria

1. Catalases

2. Peroxidase

Enzymes that can break down Hydrogen Peroxide

Catalases

(Enzyme that can break down Hydrogen Peroxide)

Can decompose toxic hydrogen peroxide to water and oxygen

Peroxidases

(Enzyme that can break down Hydrogen Peroxide)

Convert hydrogen peroxide into water

1. Superoxide Dismutase

2. Antioxidants (like Vitamins C & E)

What two things do aerobes possess that can reduce the toxic forms of oxygen?

Facultative Anaerobes

(Organisms based on Oxygen Requirement)

• Can survive with or without oxygen

• Some aerobic organisms can maintain life via fermentation or anaerobic respiration

1. Escherichia Coli

2. Few yeasts

3. Many prokaryotes

Examples of Facultative Anaerobes

Aerotolerant Anaerobes

(Organisms based on Oxygen Requirement)

• Do not use aerobic metabolism (use anaerobic respiration) but tolerate O2 by having some of the enzymes that detoxify oxygen’s poisonous forms

• Metabolism is fermentative

  • Fermentation is during glycolysis only

  • Uses organic molecules as electron acceptor and oxygen is not needed in this process

1. Lactobacilli

2. Many Prokaryotes

3. Few Protozoans

Examples of Aerotolerant Anaerobes

Microaerophiles

(Organisms based on Oxygen Requirement)

• Organisms that require O2 levels of 2-10%

• Grow only when oxygen levels are low (oxygen content lower than that which is present in the air) because they lack enzymes for detoxification (do not have peroxidases)

1. Campylobacter Jejuni

2. Helicobacter Pylori

Examples of Microaerophiles

Helicobacter Pylori

Example of Microaerophile that is a normal flora in the stomach but is opportunistic and becomes ulcer in the stomach

1. Protein

2. Ammonium

3. Nitrogen Gas

What are sources of nitrogen for most bacteria?

Nitrogen

• Essential element contained in many organic compounds, including the amine group of amino acids and as part of the nucleotide bases

• 14% of the dry weight of microbial cells

• Growth-limiting nutrients because anabolism ceases when insufficient

• Cells also recycle this from their amino acids and nucleotides

Nitrogen Fixation

Process in which few bacteria (many cyanobacteria and rhizobium) reduce N2 gas to ammonia (NH3)

Nitrogenase

Enzyme that facilitates nitrogen fixation and converts atmospheric nitrogen into ammonia

1. Phosphorus

2. Sulfur

3. Growth Factors

   1. B-Complex Vitamins

   2. Amino Acids

   3. Purines & Pyrimidines

   4. Yeast extract, blood, or serum

Organic compounds needed by organisms which is essential but the bacteria cannot provide therefore are commercially incorporated in the culture media

Phosphorus

• Component of phospholipid membranes, DNA, RNA, ATP, and some proteins

• Sources are mainly:

  • Inorganic salts

  • Buffer

Sulfur

• Component of sulfur-containing amino acids which bind to one another via disulfide bonds critical to the tertiary structure of proteins and vitamins, such as thiamine (B1) and biotin

• Sources:

  • Protein

  • Hydrogen Sulfide

  • Salts that dissociate to form sulfates

1. B-complex vitamins

2. Amino acids

3. Purine & pyrimidines

4. Yeast extract, whole blood, serum

Growth Factors

B-Complex Vitamins

(Growth Factor)

• Serve as coenzymes (help enzymes in catalyzing)

Amino Acids

(Growth Factor)

• For manufacture of proteins

Purines & Pyrimidines

(Growth Factor)

• For synthesis of nucleic acids

Yeast Extract, Whole Blood, Serum

(Growth Factor)

• Can be incorporated into culture medium

1. Temperature

2. pH

3. Water

4. Carbon Dioxide

Physical Requirements

1. Psychrophiles or Cryophiles

2. Mesophiles

3. Thermophiles

Organisms classified based on preferred temperature

Psychrophiles or Cryophiles

(Organisms classified based on preferred temperature)

• Cold-loving

• Can grow at a range of 0-20 degrees celsius

• Reason why even food inside the refrigerator can spoil

1. Algae

2. Fungi

3. Bacteria in snowfields, ice, and cold water

Examples of psychrophiles or cryophiles

Mesophiles

(Organisms classified based on preferred temperature)

• Most bacteria belong in this classification

• Grow best at 20-40 degrees Celsius (optimum: 37 degrees Celsius)

• Includes

  • Human pathogens and common spoilage organisms

  • Thermoduric organisms

  • Pasteurization-surviving bacteria

Thermoduric Organisms

Mesophile that can withstand high temperatures and even sterilization in the canning industry

37 degrees Celsius

Optimal temperature for mesophiles, including thermoduric organisms

Pasteurization

Process in which certain packages and non-packaged foods are treated with mild heat to eliminate pathogens and extend shelf-life

1. Bacillus

2. Clostridium

3. Enterococci

Specific species of bacteria that are thermoduric

Thermophiles

(Organisms classified based on preferred temperature)

• Heat loving

• Grow at temperatures above 45 degrees Celsius

• Some form extremely heat resistant endospores

• Includes some members of archae (hyperthermophiles) which grow in water above 80 degrees celsius, some above 100 degrees celsius

Hyperthermophiles/Extreme Thermophiles

Some members of archae that grow in water above 80 degrees Celsius, some above 100 degrees Celsius

Pyrodictium

What is the record holder hyperthermophiles, which survive at 113 degrees Celsius and can survive for an hour at 121 degrees Celsius?

45 degrees celsius

Optimal temperature for thermophiles

6.5-7.5

What is the pH range most bacteria prefer?

5 & 6

What is the pH molds and yeast prefer?

1. Neutrophiles

2. Acidophiles

3. Alkalinophiles

Organisms classified based on pH

Neutrophiles

(Organisms classified based on pH)

• Most bacteria and protozoans, including most pathogens that grow in a narrow range around pH 6.5-7.5

Acidophiles

(Organisms classified based on pH)

• Able to live and thrive is pH below 6

Chemoautophic Bacteria

Example of acidophile that lives in mines and water that runs off from mine tailings, which oxidize sulfur to sulfuric acid, lowering further the pH of the environment

Extremophiles

Most chemoautotrophs are this, which live in hostile environments, such as deep sea vents and are primary producers in such ecosystems

1. Hydrogen Sulfide

2. Elemental Sulfur

3. Ferrous Ion

4. Hydrogen

5. Ammonia

Chemoautrophic bacteria use these inorganic energy sources

Lactobacilli

Example of acidophile that can produce lactic acid and can tolerate mild acidity

Alkalinophiles

(Organisms classified based on pH)

• Live and thrive in alkaline conditions, which most bacteria cannot do

• Can survive in soils and water up to pH 11.5

• Also called extremophiles that can grow optimally in a pH 9-11

1. Vibrio Cholerae

2. Alcaligene Faecalis

3. Soil Bacterium and Agro Bacterium

Examples of Alkalinophiles

Vibrio Cholerae

Example of alkalinophile that grows best outside the body in water at pH 9.0

Soil Bacterium & Agro Bacterium

Example of alkalinophile that grows best in pH of 12

80%

Bacteria is made of how much percent of water?

Mycobacterium Tuberculosis

Bacteria that have cell walls that retain water so that they can survive for months under dry conditions