Bacteria Characteristics and Types

Characteristics of Bacteria

• Prokaryotic cells: Lack true nucleus and membrane-bound organelles
• Single-celled: Typically 0.5-5.0 μm in diameter
• Cell wall: Rigid layer outside cell membrane, provides shape and support
• Flagella: Whip-like structures used for movement

Types of Bacteria

• Gram-positive: Thick peptidoglycan layer in cell wall, stain purple
• Gram-negative: Thin peptidoglycan layer, outer membrane, stain pink
• Spiral (e.g., Spirillum): Helical shape, often found in aquatic environments
• Rod-shaped (e.g., E. coli): Straight or curved, common in soil and human gut
• Spherical (e.g., Staphylococcus): Round shape, often found in skin and respiratory tract

Bacterial Growth and Reproduction

• Binary fission: Cell division, resulting in two identical daughter cells
• Generation time: Time required for population to double in size
• Nutrient requirements: Carbon, nitrogen, phosphorus, and other elements for growth
• Environmental factors: Temperature, pH, oxygen, and light affect growth and survival

Bacterial Metabolism

• Aerobic: Use oxygen for energy production (e.g., Pseudomonas)
• Anaerobic: Do not use oxygen for energy production (e.g., Clostridium)
• Fermentation: Break down organic compounds to produce ATP and byproducts
• Nitrogen fixation: Convert atmospheric nitrogen into usable forms

Interactions with Environment and Hosts

• Symbiotic relationships: Mutualism (e.g., gut bacteria), commensalism, or parasitism
• Pathogenesis: Ability to cause disease in hosts (e.g., Salmonella, Streptococcus)
• Antibiotic resistance: Development of mechanisms to evade antibiotic effects
• Biofilm formation: Adhesion to surfaces, forming complex communities

Characteristics of Bacteria

• Lack true nucleus and membrane-bound organelles, making them prokaryotic cells
• Typically 0.5-5.0 μm in diameter, being single-celled organisms
• Possess a rigid cell wall outside the cell membrane, providing shape and support
• Have whip-like flagella structures used for movement

Types of Bacteria

• Gram-positive bacteria have a thick peptidoglycan layer in their cell wall and stain purple
• Gram-negative bacteria have a thin peptidoglycan layer, an outer membrane, and stain pink
• Spiral bacteria, such as Spirillum, have a helical shape and are often found in aquatic environments
• Rod-shaped bacteria, like E. coli, are straight or curved and common in soil and the human gut
• Spherical bacteria, such as Staphylococcus, have a round shape and are often found in skin and the respiratory tract

Bacterial Growth and Reproduction

• Bacteria reproduce through binary fission, resulting in two identical daughter cells
• The generation time is the time required for the population to double in size
• Bacteria require carbon, nitrogen, phosphorus, and other elements for growth
• Environmental factors like temperature, pH, oxygen, and light affect growth and survival

Bacterial Metabolism

• Aerobic bacteria, such as Pseudomonas, use oxygen for energy production
• Anaerobic bacteria, like Clostridium, do not use oxygen for energy production
• Fermentation is the process of breaking down organic compounds to produce ATP and byproducts
• Nitrogen-fixing bacteria convert atmospheric nitrogen into usable forms

Interactions with Environment and Hosts

• Symbiotic relationships can be mutualistic, commensalistic, or parasitic
• Pathogenic bacteria, like Salmonella and Streptococcus, have the ability to cause disease in hosts
• Antibiotic resistance occurs when bacteria develop mechanisms to evade antibiotic effects
• Biofilm formation involves the adhesion of bacteria to surfaces, forming complex communities