VPBacteriology_Bacteria_Metabolism_Phylogeny_Pathogenesis_DrGutierrez_Spring2024.pdf

VPRP096 Introduction to Microbiology: Bacterial Metabolism, Phylogeny & Pathogenesis Dr. Ricardo Gutiérrez, Microbl., MSc, Ph.D. Assistant Professor [email protected] Spring semester, 2024 Bacterial growth and metabolism Metabolism Metabolism is defined as the sum of all chemical reactions r...

VPRP096 Introduction to Microbiology: Bacterial Metabolism, Phylogeny & Pathogenesis Dr. Ricardo Gutiérrez, Microbl., MSc, Ph.D. Assistant Professor [email protected] Spring semester, 2024 Bacterial growth and metabolism Metabolism Metabolism is defined as the sum of all chemical reactions required to support cellular function and hence the life of an organism Metabolism G O A L S ANABOLISM CATABOLISM Energy transfer Matter transport Cellular work Growth and reproduction Bacterial growth and metabolism Metabolism energy ATP Adenosine triphosphate Bacterial growth and metabolism Bacterial growth: Bacteria replicate by binary fission BINARY FISSION Bacterial growth and metabolism Bacterial growth: Bacteria replicate by binary fission Generation time Length of time required for a single bacterial cell to yield two daughter cells (30 min to 20h) T I M E BINARY FISSION Bacterial growth and metabolism Bacterial growth: Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g., glucose, nitrates, fatty acids) Ionic strength & osmotic pressure Temperature Gaseous requirement (oxygen, carbon dioxide) Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g. glucose, nitrates, fatty acids) Ionic strength & osmotic pressure Temperature Gaseous requirement (oxygen, carbon dioxide) Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g., glucose, nitrates, fatty acids) Ionic strength & osmotic pressure Temperature Gaseous requirement (oxygen, carbon dioxide) Nutrients are needed for energy production and as molecule sources Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g., glucose, nitrates, fatty acids) Ionic strength & osmotic pressure Temperature Gaseous requirement (oxygen, carbon dioxide) 2 – 4 ATPs Fermentation (anaerobic respiration) Aerobic respiration Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g., glucose, nitrates, fatty acids) Ionic strength & osmotic pressure H+ H+ H+ + + + H+ H H+ H + H H H+ + H+ H+ H+H H+ - OH-OHOH -OHOH -OH- OH-OHOH-OH-OH OH- OHOH OH- Temperature Gaseous requirement (oxygen, carbon dioxide) Most pathogenic bacteria grow best at neutral pH (7.0). Some are acid tolerant and can survive the harsh conditions of the stomach. Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g., glucose, nitrates, fatty acids) Ionic strength & osmotic pressure Temperature Gaseous requirement (oxygen, carbon dioxide) Most pathogenic bacteria grow best at osmotic pressures equivalent to physiological saline (0.65% NaCl). Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g., glucose, nitrates, fatty acids) Ionic strength & osmotic pressure Temperature Gaseous requirement (oxygen, carbon dioxide) Temperature requirement for optimal enzyme-catalyzed metabolic reactions. Most pathogenic bacteria are mesophiles. Bacterial growth and metabolism Bacterial growth: Specific environmental factors are required for the process to occurs Nutrients F A C T O R S pH (e.g., glucose, nitrates, fatty acids) Ionic strength & osmotic pressure Temperature Gaseous requirement (oxygen, carbon dioxide) Bacteria vary in their need and tolerance for oxygen. They are divided into two major groups: aerobes and anaerobes. The carbon dioxide is required for growth. The air levels are sufficient for many bacteria (0.04%). Some require elevated levels of carbon dioxide (5-10%). Bacterial growth and metabolism Bacterial growth The size of bacteria populations is expressed as the number of cells present. Bacterial growth and metabolism Bacterial growth curve Nutrient exhaustion & accumulation of toxic products SPORE FORMATION Progressive death of cells Cells multiply at maximum rate Increase in cell size, active metabolism of cells but no division Bacterial growth curve with 4 phases (in liquid medium) Bacterial growth and metabolism The result: (over)multiplication of bacteria in the wrong place → disease Phylogeny Phylogeny Phylogenetic tree Diagram representing evolutionary relationships among organisms Common ancestor of all life Based on comparative gene sequence analyses of conserved genes (rRNA genes) Recent development towards whole genome-based phylogeny Phylogeny Applications Phylogeny Taxonomy Study of bacterial identification, nomenclature and classification Permits accurate identification Precise naming for efficient communication Group similar organisms Species Basic taxonomic unit Group or population composed of similar individuals that are capable of interbreeding naturally and are reproductively isolated from other groups Escherichia coli Genus species Phylogeny Taxonomy Bacillus subtilis Bacillus cereus Bacillus anthracis Mostly non-pathogenic Food-poisoning pathogen Lethal pathogen Phylogeny Taxonomy Polyphasic taxonomy: Classification of bacteria as evaluated by both genotypic, phylogenetic and phenotypic properties Bacterial Pathogenesis Bacterial (biological) mechanisms that lead to a disease “how do bacteria cause disease?” Bacterial pathogenesis HOST Susceptible host Breed age, sex, genotype Physiology and ‘damage’ Immunity PATHOGEN DISEASE Pathogen Environment Pathogenicity (ability to cause disease) Virulence (measurement of pathogenicity) Infection route, tropism Inoculation dose Virulence factors (bacterial characteristics that contribute to virulence) ENVIRONMENT Housing, management, hygiene Nutrition Disease control Bacterial pathogenesis Pathogen I will! Because I need to! Obligate pathogen Maybe I Will! Facultative pathogen Just give me the opportunity! Opportunistic pathogen Infectious agent: a microorganism that can cause disease upon colonization of the host Obligate pathogen: it must infect a host and cause disease to multiply and be transmitted from one host to another Facultative pathogen: it can infect and multiply in hosts but is also capable of multiplying in the environment Opportunistic pathogen: microorganism which does not ordinarily cause disease but which, under certain conditions (e.g., impaired host immunity) becomes pathogenic Bacterial pathogenesis Host-Pathogen interaction Defined as how bacteria (and other pathogens) sustain themselves within host organisms on a molecular, cellular, organismal or population level. Host Environment Bacterial pathogenesis Host-Pathogen interaction EXPOSURE ADHESION INVASION Infection: the invasion and/or multiplication of pathogens in an individual host COLONIZATION Until here the infection occurred. The consequence can be: Commensal interaction Mutualistic relationship Disease Only in invasive strains… COLONIZATION Until here “disease” has occurred Bacterial pathogenesis The pathogen path… Express genes (virulence factors) that code for factors causing disease DISEASE Overcome host defense Compete microbiota to adhere to host cells Find susceptible host and appropriate niche within host PATHOGEN Bacterial pathogenesis Infectious disease A disease (a disorder of structure or function in the host) caused by pathogens and transmittable to other hosts Bacterial pathogenesis Stages of the infection exposure Bacterial pathogenesis Infection outcomes No colonization Infection → disease → recovery Infection → subclinical disease Infection → disease → death/disability Infection → disease → persistence (carriers) Bacterial pathogenesis Inflammation Biological host response to harmful stimuli such as pathogens and/or their metabolites. A defensive response governed primarily by the immune system, which dispatches white blood cells to the affected sites, resulting in redness and swelling or symptoms such as fever. Results: Local tissue damage (due to toxins and/or immune response) Toxemia Acute systemic disease Chronic disease Bacterial pathogenesis Iceberg concept of disease Severe diseases and death Mild illness Subclinical disease