BIO-3203 Bacterial Species_2024 DWF

BACTERIAL SPECIES

Classification

  • Prokaryotes divided into two main categories:

    • Bacteria

      • Further divided into:

        • Proteobacteria

          • Gram-negative

          • Gram-positive

        • Atypical Bacteria

        • Photobacteria

    • Archaea

DIVERSITY AND HABITATS

  • Prokaryotes can survive in diverse habitats, including:

    • Very cold environments

    • Very hot conditions

    • Extreme pressure scenarios

  • There are ten times more bacteria in the human body than human cells.

  • Bacteria can be found in:

    • Gastrointestinal tract

    • Skin

    • Ears

    • Respiratory tract

    • Vagina

  • Most prokaryotic organisms are not pathogenic.

  • Many bacterial species in soil coexist commensally with plants and animals.

  • Prokaryotes can also exist in the air.

CONFUSIONS ABOUT BACTERIA

  • Each bacterium typically thrives in a very specific environment (e.g., skin, gut, dirt, ocean).

  • Dramatic changes to their environment often lead to death.

    • Example: Raising meat temperature from 90°F to 165°F.

    • Example: Drying a surface with alcohol or ammonia (e.g., Lysol).

  • Bacteria can adapt and evolve rapidly, but might not thrive outside their typical environment.

  • Example: A new species discovered at Chernobyl feeds off radiation, indicating possible survival in extreme conditions (like space).

TYPES OF SYMBIOSIS

  • Mutualism: Both populations benefit.

  • Commensalism: One population benefits; the other is unaffected.

  • Amensalism: One population benefits; the other is harmed.

  • Neutralism: Neither population is affected.

  • Parasitism: One population benefits at the expense of the other.

BACTERIAL METABOLISM

  • Most bacteria perform anaerobic glycolysis, which produces:

    • Pyruvate & NADH, needing removal.

    • Conversion to lactate or alcohol + CO2.

  • Testing will include:

    • Lactate detection

    • Alcohol/CO2 detection

  • Bacteria relying on anaerobic metabolism require large amounts of sugar.

  • Some can switch between anaerobic and aerobic metabolism.

  • Requires oxidase enzymes for electron transfer and energy production.

  • Testing will include:

    • Oxidase detection

    • Lipid hydrolysis testing

ADVANTAGES OF PROKARYOTES

  • Ability to adapt metabolism based on environmental conditions:

    • Carbon fixation: Capturing carbon from CO2 to create organic compounds.

    • Nitrogen fixing: Converting atmospheric nitrogen into usable forms (e.g., ammonia).

      • Notable species include Rhizobium (in legumes).

  • Helpful in cleaning up toxic chemicals in polluted environments.

    • Certain species exist in manmade polluted areas.

NITROGEN-FIXING BACTERIA

  • Convert atmospheric nitrogen gas to ammonia, which plants can use.

  • Examples of nitrogen-fixing bacteria:

    • Rhizobium (in legumes)

    • Azotobacter (free-living)

    • Frankia (in actinorhizal plants)

    • Cyanobacteria like Anabaena and Nostoc.

  • Use nitrogenase enzyme; sensitive to oxygen levels, thus often need low oxygen environments.

METABOLISM WITHOUT OXYGEN

  • Glycolysis functions in both aerobic and anaerobic conditions.

  • NAD+ is needed for glycolysis, regenerated during oxidative phosphorylation with O2.

  • Without O2, fermentation regenerates NAD+:

    • Types of fermentation:

      • Lactic acid fermentation

      • Alcohol fermentation

LACTIC ACID FERMENTATION

  • Occurs under limited O2 in muscle cells, red blood cells, and some bacteria (e.g., yogurt).

  • Reaction:

    • Pyruvate + NADH ⇌ Lactate + NAD+

ALCOHOL FERMENTATION

  • Conducted by anaerobic yeast; involves:

    • Two reactions:

      1. First: Pyruvate → CO2 + Acetaldehyde

      2. Second: Acetaldehyde + NADH → Ethanol + NAD+

ATP PRODUCTION

Methods:

  • Substrate Level Phosphorylation

  • Cellular Respiration (Oxidative Phosphorylation)

  • Photosynthesis

RESPIRATION OVERVIEW

  • Cellular respiration extracts energy from food to generate ATP:

    • Phases:

      1. Harvesting electrons from carbon-carbon bonds (Citric Acid Cycle)

      2. Using electrons to power oxidative phosphorylation (Electron Transport Chain)

REDOX REACTIONS

  • Electron carriers are vital in cellular respiration and photosynthesis, shuttling electrons in transport chains to produce ATP.

    • Examples:

      • NAD+, FAD+

      • NADH, FADH2

  • NADH carries more electrons and is an essential electron donor.

TYPES OF BACTERIAL OXIDATION

  • Iron oxidation:

    • Iron-oxidizing bacteria derive energy from oxidizing dissolved iron, thrive in high-iron waters.

  • Sulfur oxidation:

    • Use inorganic sulfur compounds as an energy source.

  • Ammonia oxidation:

    • Essential in the nitrogen cycle, oxidizing ammonia to nitrite as the first step in nitrification.

PHOTOTROPHIC BACTERIA

  • Photosynthetic, not necessarily related.

    • May have varied photosynthetic capabilities.

    • Examples:

      • Proteobacteria

      • Non-proteobacteria

  • Perform oxygenic or anoxygenic photosynthesis.

  • Utilize bacteriochlorophylls for photosynthesis.

GROWTH AND OPTIMIZATION

  • Photoautotrophs: Depend on light for growth (e.g., cyanobacteria).

  • Photoheterotrophs: Energy from light, capture energy to drive CO2 fixation.

  • Bacterial growth aligns with optimal conditions including:

    • pH levels

    • Temperature ranges

BACTERIAL GROWTH CURVES

  • Growth indicates phases:

    1. Lag Phase - adjustment to the environment.

    2. Log Phase - exponential growth.

    3. Stationary Phase - stable growth due to space and resources.

    4. Death Phase - decline in cell numbers.

BINARY FISSION

  • The primary method of bacterial reproduction:

    • Steps:

      1. DNA replication as the cell elongates.

      2. Formation of a division septum in the center.

      3. Two daughter cells form and separate.

ACIDITY AND GROWTH

  • Optimum pH: Best growth level.

  • Minimum pH: Threshold between growth and death.

  • Maximum pH: Extreme tolerable value.

  • Different bacteria prefer different pH levels:

    • Most are neutrophiles.

    • Acidophiles: Thrive at low pH (e.g., Lactobacillus).

TEMPERATURE AND GROWTH

  • Microbes categorized by optimal growth temperatures:

    • Mesophiles: Grow best around 37 °C (human body).

    • Psychrotrophs: Favor cooler temperatures, causing spoilage in refrigeration.

TYPES OF BACTERIA

Gram-Negative Bacteria

  • Examples:

    • Spirochetes (causes syphilis, Lyme disease)

    • CFB Group: Cytophaga, Fusobacterium, Bacteroides.

Gram-Positive Bacteria

  • High GC: Actinobacteria (e.g., Mycobacteria, Corynebacterium).

  • Low GC: Clostridia (e.g., C. perfringens, C. botulinum).

DEEPLY BRANCHING BACTERIA

  • Definition: Ancient prokaryotic organisms believed to be common ancestors of existing life.

ARCHAEA

  • Characteristics:

    • Unicellular and non-pathogenic.

    • Unique cell membrane linkages and pseudopeptidoglycan cell walls.

    • Two main types:

      • Mesophiles: Temperate habitats.

      • Extremophiles: Extreme habitats.

SUMMARY

  • Prokaryotes thrive in various habitats, are unicellular, and can form different arrangements.

  • Classification as Gram-negative (Proteobacteria, non-proteobacteria) and Gram-positive (high GC and low GC).

  • Archaea represent a unique group, distinct from bacteria, with no pathogenic species.