Download MICR 201 Microbiology for Health Related Sciences

Lecture 5: Survey of the microbial world
Edith Porter, M.D.
1
 Classification of microorganisms
▪ Taxonomy
▪ Three domain system: Bacteria, Archaea, Eukarya
 Prokaryotes
▪ Bacteria
▪ Archaea
 Eukaryotes
▪ Protozoa
▪ Algae
▪ Fungi
▪ Helminths
2
3





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)
4


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
5
6
7
8
9
10




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
11
12
13



Obligate intracellular bacteria
Cannot proliferate outside of a host cell
Selected human pathogens
 Rickettsia
 Chlamydia
14



Transmitted by ticks or lice
Infects vascular endothelial cells
R. rickettsii: Rocky Mountain spotted fever
http://www.lincolner.com/Lincoln
%20page%203/images/rocky%2
0mountain%20spotted%20fever
1.jpg
15
16
17
18





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
19
, absorptive
20
YEASTS



Unicellular
Proliferate by budding or
fission
Candida albicans
MOLDS




Multicellular
Septated and unseptated
hyphae
Mass of hyphae is mycelium
Aspergillus spec., Rhizopus
spec.
21
Switch growth phase depending on environmental
conditions
 Pathogenic dimorphic fungi are yeastlike at 37°C and
moldlike at 25°C

22






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!
23

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
24
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
25





Archaezoa: Trichomonas, Giardia
Amaebazoa: Entamoeba
Apicomplexa: Plasmodium
Ciliophora: Balantidum
Euglenozoa: Trypanosoma
26
27
28



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
29
30

Monoecious (hermaphroditic)
 Male and female reproductive systems in one
animal

Dioecious
 Separate male and female

Egg  larva(e)  adult
31

Oral sucker: food uptake
 Incomplete digestive tract


Ventral Sucker: Attachment
Mostly hermaphroditic (monoecious)
32
33


Sucker for
attachment
No digestive tract
 Food uptake by
absorption


Hermaphrodites
(monoecious)
Scolex, neck,
proglottides
34
Necator americanus
(hook worm)



Dioecious (male, female)
Complete digestive tract
Caenorrhabditis elegans: model system
35

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
36



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
37