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 Ribosomal RNA sequences Phylogenetic analysis

Bacteria Archaea Eu k aryotes Plants Animals Fungi Protozoa Prokaryotes Eukarya Algae Classification of living organisms

Prokaryotes and Eukaryotes

CharacteristicProkaryotic cellEukaryotic cell Size of cellTypically  m in diameter Typically  m in diameter Nuclear membrane AbsentPresent NucleolusAbsentPresent Membrane- enclosed organell e s AbsentPresent (lysosomes, Golgi complex, ER, mitochondria, and chloroplasts)

Prokaryotes and Eukaryotes CharacteristicProkaryotic cellEukaryotic cell Cell wallUsually present; chemically complex When present, chemically simple Plasma membrane No carbohydrates; generally lacks sterols Carbohydrates and sterols are present Ribosomes70S80S DNASingle circular chromosome; lacks histones Multiple linear chromosomes; histones are present

Prokaryotes and Eukaryotes CharacteristicProkaryotic cellEukaryotic cell Cell divisionBinary fissionMitosis Sexual reproduction No meiosis; transfer of DNA fragments only Involves meiosis Cellular respiration Cell membraneMitochondria Endospore formation PresentAbsent

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

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 N 2 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

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 ( ): 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 ( ): 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