370 likes | 574 Views
Lecture 5: Survey of the microbial world Edith Porter, M.D. MICR 201 Microbiology for Health Related Sciences. Lecture Outline. Classification of microorganisms Taxonomy Three domain system: Bacteria, Archaea , Eukarya Prokaryotes Bacteria Archaea Eukaryotes Protozoa Algae Fungi
E N D
Lecture 5: Survey of the microbial world Edith Porter, M.D. MICR 201 Microbiology for Health Related Sciences
Lecture Outline • Classification of microorganisms • Taxonomy • Three domain system: Bacteria, Archaea, Eukarya • Prokaryotes • Bacteria • Archaea • Eukaryotes • Protozoa • Algae • Fungi • Helminths
Taxonomy • The science of classifying organisms • Provides universal names for organisms • Provides a reference for identifying organisms • Initially based on morphology and biochemical assays • Now based on nucleic acid sequencing (16S and 18S rRNA analysis)
Phylogeny (or systematics) • The study of the evolutionary history of organisms • All Species Inventory (2001–2025) • To identify all species of life on Earth • Species definition • Eukaryotes: breed among themselves • Prokaryotes: > 97% homology in 16S rRNA • Cladograms used to establish relation ship
Cladogram to Establish the Evolutionary Relationship of Microorganisms
Important to Remember • Taxonomy is the science of classification using a hierarchical system • Universal ancestor • The three domains differ in presence of a nucleus (eukarya), ether linked lipids (archaea) and use of formylmethionine as started amino acid in protein synthesis (bacteria) • Cladograms are used to establish evolutionary relationships
Selected bacterial life forms • Obligate intracellular bacteria • Cannot proliferate outside of a host cell • Selected human pathogens • Rickettsia • Chlamydia
Rickettsia • Transmitted by ticks or lice • Infects vascular endothelial cells • R. rickettsii: Rocky Mountain spotted fever http://www.lincolner.com/Lincoln%20page%203/images/rocky%20mountain%20spotted%20fever1.jpg
Fungi • Eukaryotic • Aerobic or facultatively anaerobic • Chemoheterotrophic • Most are decomposers • Asexual and sexual spore formation • For Reproduction, not endurance!! • Broad use of fungi • Food, food production, drugs • Mycology is the study of fungi
Comparison of fungi and bacteria , absorptive
Yeast and molds Yeasts Molds Multicellular Septated and unseptatedhyphae Mass of hyphae is mycelium Aspergillus spec., Rhizopus spec. • Unicellular • Proliferate by budding or fission • Candida albicans
Dimorphic fungi • Switch growth phase depending on environmental conditions • Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C
Fungal diseases • Systemic mycoses: Deep within body • Subcutaneous mycoses: Beneath the skin • Cutaneous mycoses: Affect hair, skin, and nails • Superficial mycoses: Localized, e.g., hair shafts • Opportunistic mycoses: Caused by normal microbiota or environmental fungi • Note: antibiotics do not work against fungi!
Medically relevant fungi • Yeasts • Candida: Candidiasis • Cryptococcus: Meningitis • Molds • Aspergillus: Lung infection in neutropenic patients • Rhizopus, Mucor: in diabetes patients • Dimorphic • Coccidioides: Lung infections • Histoplasma: Lung infections • Dermatophytes • Trichophyton, Epidermophyton: Tinea
Protozoa • Eukaryotic • Always unicellular • Chemoheterotrophs • Digestion in vacuoles • Often complex life cycles with multiple hosts and vectors • Some produce cysts • Resistant survival forms • Vegetative form is a trophozoite • Reproduction • Asexual • Sexual reproduction
Medically Important Phyla of Protozoa • Archaezoa: Trichomonas, Giardia • Amaebazoa: Entamoeba • Apicomplexa: Plasmodium • Ciliophora: Balantidum • Euglenozoa: Trypanosoma
Characteristics of Helminths • Eukaryotic • Multicellular, organ differentiation • Kingdom: Animalia • Phylum: Platyhelminthes (flatworms) • Class: Trematodes (flukes) • Class: Cestodes (tapeworms) • Phylum: Nematodes (roundworms) • Chemoheterotrophic • Multiple hosts • Intermediate host • Definitive host: adult form develops, sexual reproduction
Life Cycle of Helminths • Monoecious (hermaphroditic) • Male and female reproductive systems in one animal • Dioecious • Separate male and female • Egg larva(e) adult
Trematodes (Flukes) • Oral sucker: food uptake • Incomplete digestive tract • Ventral Sucker: Attachment • Mostly hermaphroditic (monoecious)
Cestodes(Tape Worms) • Sucker for attachment • No digestive tract • Food uptake by absorption • Hermaphrodites (monoecious) • Scolex, neck, proglottides
NematodesRoundworms Necator americanus (hook worm) • Dioecious (male, female) • Complete digestive tract • Caenorrhabditiselegans: model system
Important to Remember • Fungi • Molds (septated, unseptated), yeast, dimorphic • Sexual and asexual spores • Mycoses: local or systemic impairment of host defense • Protozoa: always unicellular, often vectors • Helminths: always multicellular, complex life cycles
Helminths • Eukaryotic • Multicellular, organ differentiation • Kingdom: Animalia • Phylum: Platyhelminthes (flatworms) • Class: Trematodes (flukes) • Class: Cestodes (tapeworms) • Phylum: Nematodes (roundworms) • Chemoheterotrophic • Multiple hosts • Intermediate host • Definitive host: adult form develops, sexual reproduction