1

MICR 201 Microbiology for Health Related Sciences

Lecture 5: Survey of the microbial worldEdith Porter, M.D.

2

Lecture Outline

Classification of microorganisms▪ Taxonomy▪ Three domain system: Bacteria, Archaea,

Eukarya Prokaryotes▪ Bacteria▪ Archaea

Eukaryotes▪ Protozoa▪ Algae▪ Fungi▪ Helminths

3

Classification of microorgansims

4

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)

5

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

6

Cladogram to Establish the Evolutionary Relationship of Microorganisms

7

Three domain system (Carl Woese)

8

Model of the origin of eukaryots

9

Major differences between domains (1)

10

Major differences between domains (2)

11

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

12

Prokaryotes

13

The Prokaryotes

14

Selected bacterial life forms

Obligate intracellular bacteria Cannot proliferate outside of a host

cell Selected human pathogens

Rickettsia Chlamydia

15

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

16

Chlamydia (1)

17

Chlamydia (2)

18

Eukaryotes

19

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

20

Comparison of fungi and bacteria

, absorptive

21

Yeast and molds

YEASTS Unicellular Proliferate by budding

or fission Candida albicans

MOLDS Multicellular Septated and unseptated

hyphae Mass of hyphae is

mycelium Aspergillus spec.,

Rhizopus spec.

22

Dimorphic fungi

Switch growth phase depending on environmental conditions

Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C

23

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!

24

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

25

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

26

Medically Important Phyla of Protozoa

Archaezoa: Trichomonas, Giardia Amaebazoa: Entamoeba Apicomplexa: Plasmodium Ciliophora: Balantidum Euglenozoa: Trypanosoma

27

Life cycle of Plasmodium vivax

28

Helminths

29

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

30

31

Life Cycle of Helminths

Monoecious (hermaphroditic) Male and female reproductive systems in

one animalDioecious

Separate male and femaleEgg larva(e) adult

32

Trematodes (Flukes)

Oral sucker: food uptake Incomplete digestive tract

Ventral Sucker: Attachment Mostly hermaphroditic (monoecious)

33

Life Cycle of Paragonimus westermani (Lung fluke)

34

Cestodes(Tape Worms)

Sucker for attachment

No digestive tract Food uptake by

absorption Hermaphrodites

(monoecious) Scolex, neck,

proglottides

35

NematodesRoundworms

Dioecious (male, female) Complete digestive tract Caenorrhabditis elegans: model system

Necator americanus (hook worm)

36

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

37

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