Bacterial Metabolism/Phylogeny
Bacterial Growth and Metabolism
Metabolism
Defined as the sum of all chemical reactions necessary to support cellular functions and organismal life.
Key components:
Energy transfer
Matter transport
Cellular work
Growth and reproduction
Divided into two main processes:
Anabolism: Building up molecules.
Catabolism: Breaking down molecules to release energy.
Energy Carrier
ATP (Adenosine Triphosphate): Key energy currency for cellular metabolism.
Structure:
Contains adenine, phosphate groups, and ribose sugar.
Releases energy when phosphate groups are hydrolyzed.
Bacterial Replication
Binary Fission
Process by which bacteria replicate.
Steps involved in Binary Fission:
Cell elongates and the nucleoid divides.
Cell wall and membrane begin to constrict forming a transverse septum.
Septum becomes complete, resulting in daughter cell separation.
Generation Time
Length of time for a single bacterial cell to divide into two daughter cells, varying from 30 minutes to 20 hours.
Environmental Factors for Bacterial Growth
Essential Factors
Specific conditions that must be met for bacterial growth include:
Nutrients: Such as glucose, nitrates, fatty acids.
pH: Optimal pH for growth, most pathogenic bacteria thrive at neutral pH (7.0).
Ionic Strength & Osmotic Pressure: Physiological saline equivalence (0.65% NaCl) is optimal.
Temperature: Most pathogenic bacteria are mesophiles and require certain temperature ranges for optimal growth.
Gaseous Requirements: Oxygen and carbon dioxide levels affect growth; bacteria can be aerobes or anaerobes.
Bacterial Growth Curve
Phases
Diagram illustrating the growth curve in liquid medium.
Phases include:
Lag Phase: Increase in cell size and activity, no division.
Log Phase: Cells multiply at maximum rate.
Stationary Phase: Nutrient exhaustion and buildup of toxic products.
Death Phase: Progressive cell death and formation of spores.
Phylogeny
Phylogenetic Tree
Diagram representing evolutionary relationships among organisms, based on comparative analyses of rRNA genes and recent developments in whole genome phylogeny.
Applications of Phylogeny
Examines mutation, shedding of pathogens, immunity, and transmission.
Tracks epidemic dynamics and regional spatial dynamics.
Taxonomy
Study of bacterial identification, nomenclature, and classification facilitating accurate communication and understanding of relationships among organisms.
Species: Basic taxonomic unit composed of strains with the ability to exchange core genes.
Example: Escherichia coli as a genus and species.
Polyphasic Taxonomy
Classification based on genotypic, phylogenetic, and phenotypic properties including:
Morphology
Physiology
Genetics
Genomics
Bacterial Pathogenesis
Mechanisms of Disease
Biological mechanisms exploited by bacteria to cause disease.
Key aspects include the interaction among susceptible hosts, environmental factors, and pathogens.
Types of Pathogens
Obligate Pathogen: Requires host to multiply and transmit disease.
Facultative Pathogen: Can live in the environment or infect hosts.
Opportunistic Pathogen: Causes disease under certain conditions, such as weakened immunity.
Host-Pathogen Interaction
Defined by how pathogens multiply and survive within hosts, with infection comprising exposure, adhesion, invasion, colonization, and potential disease outcomes.
Outcomes of Infection
Varies from non-colonization, recovery, subclinical disease, to persistence or severe outcomes like death.
Inflammation
Host’s defensive response characterized by redness, swelling, and pain in reaction to harmful stimuli, resulting in tissue damage and local/systemic effects.