Download Microbial World and Classification of

Assist. Prof. Emrah Ruh
NEU Faculty of Medicine
Department of Medical Microbiology
Microbial world
 Microorganism:
 A microscopic organism consisting of a single cell or
cell cluster, including the viruses
 Microbiology:
 Study of microorganisms
 Medical microbiology:
 Study of microorganisms that cause infectious
diseases
Classification of living organisms
 Linnaeus, 1753 (two kingdoms):
 Plantae: Bacteria, fungi, algae, plants
 Animalia: Protozoa and higher animals
 Haeckel, 1865 (three kingdoms):
 Plantae: Multicellular algae and plants
 Animalia: Animals
 Protista: Microorganisms (bacteria, protozoa,
algae, molds and yeasts)
Classification of living organisms
 Whittaker, 1969 (five kingdoms):
 Plantae: Multicellular algae and plants
 Animalia: Animals
 Protista: Protozoa and single-celled algae
 Fungi: Molds and yeasts
 Monera: All bacteria (prokaryotes)
Classification of living organisms
 Woese, 1977 (three domains):
 Bacteria (eubacteria): Prokaryotes
 Archae (archaebacteria): Prokaryotes
 Eukaryotes: Protozoa, algae, fungi, plants and
animals
Ribosomal RNA sequences
Phylogenetic analysis
Classification of living organisms
Prokaryotes
Bacteria
Archaea
Eukaryotes
Eukarya
Protozoa Algae
Plants
Fungi
Animals
Classification of living organisms
Classification of living organisms
Prokaryotes and Eukaryotes
Prokaryotes and Eukaryotes
Prokaryotes and Eukaryotes
Characteristic
Prokaryotic cell
Eukaryotic cell
Size of cell
Typically 0.2-2.0
mm in diameter
Typically 10-100
mm in diameter
Nuclear
membrane
Absent
Present
Nucleolus
Absent
Present
Membraneenclosed
organelles
Absent
Present (lysosomes,
Golgi complex, ER,
mitochondria, and
chloroplasts)
Prokaryotes and Eukaryotes
Characteristic
Prokaryotic cell
Eukaryotic cell
Cell wall
Usually present;
chemically
complex
When present,
chemically simple
Plasma
membrane
No carbohydrates;
generally lacks
sterols
Carbohydrates and
sterols are present
Ribosomes
70S
80S
DNA
Single circular
Multiple linear
chromosome; lacks chromosomes;
histones
histones are
present
Prokaryotes and Eukaryotes
Characteristic
Prokaryotic cell
Eukaryotic cell
Cell division
Binary fission
Mitosis
Sexual
reproduction
No meiosis;
transfer of DNA
fragments only
Involves meiosis
Cellular
respiration
Cell membrane
Mitochondria
Endospore
formation
Present
Absent
Prokaryotes: Bacteria and archae
 Bacteria (eubacteria):
 Bacteria that are most familiar to microbiologists
(disease-causing bacteria, soil and water
bacteria, and photosynthetic bacteria)
 Archae (archaebacteria):
 Bacteria that produce methane gas, require very
high levels of salt, or require very high
temperatures
Symbiosis
Symbiosis
 Mutualism (+/+):
 Reciprocal benefit
 Commensalism (+/0):
 One organism gets benefit; the other organism
gets neither benefit nor harm
 Parasitism (+/-):
 One organism gets benefit; the other organism
gets harm
The impact of microorganisms on humans
 Agriculture
 N2 fixation, nutrient
cycling…
 Food
 Food preservation,
fermented foods…
 Biotechnology
 Production of
pharmaceuticals…
The impact of microorganisms on humans
 Normal flora of
human body
 Bacteria:
protection against
infectious
microorganisms
Microbial world
Microbial world
 Microorganisms of medical importance:
 Prokaryotes

Bacteria
 Eukaryotes

Fungi

Protozoons
 Viruses
Microbial world
 Scope of medical microbiology:
 Bacteriology
Bacteria
 Mycology
Fungi
 Parasitology
Parasites
(protozoons and helminths)
 Virology
Viruses
 Immunology
Immune system
The historical roots of microbiology
 Robert Hooke, 1664  Molds
The historical roots of microbiology
 Antoni van Leeuwenhoek, 1684  Microscope;
“animalcules”; first to see bacteria and protozoons
The historical roots of microbiology
 Louis Pasteur (1822-1895):
Downfall of “spontaneous
generation” (some life
forms arise spontaneously
from non-living matter)
 Organisms found in
putrefying materials
originate from
microorganisms present in
the air
The historical roots of microbiology
 Robert Koch (1843-1910):
 Experimental support of
“germ theory of disease”
(proof that microorganisms
can cause disease); “Koch’s
postulates”
 Growth of bacteria on solid
media
 Demonstration of the agent
of tuberculosis
The historical roots of microbiology
 Alexander Fleming, 1928  Discovery of
penicillin
The historical roots of microbiology
 John Enders, 1946  Cultivation of viruses in
cell cultures