MICR501 Week 1 - Introduction to Microbial Life

Microorganism

Any organism you cannot see with the naked eye; only using a microscope

Eukaryotes

Cells with complex internal structures, including a nucleus

Eukaryote examples

Protists, Fungi, Algae

Prokaryotes

Single-celled organisms without a nucleus or membrane-bound organelles

Bacteria

Single-celled prokaryotes with diverse metabolic capabilities

Prokaryote/bacteria examples

Proteobacteria, cyanobacteria, firmicutes

Archaea

Prokaryotic microorganisms similar in size and shape to bacteria but genetically distinct, often thrive in extreme environments

Archaea examples

Euryarchaeota, crenarchaeota, halobacteria

Viruses

Microscopic infectious agents

Virus structure

Genetic material enclosed in a protein coat

Types of microscopes

Dissecting microscope, compound microscope, fluorescent microscope, electron microscope

Brightfield microscopy

Light passes through objects, samples often need to be stained

Brightfield microscopy view

Specimen is dark on light background, samples often need to be stained

Darkfield microscopy

Light is reflected off the objects, good for observing microbial cells unstained; particularly useful for live cells

Darkfield microscopy view

Specimen is light on a dark background, shows minute details better

Fluorescent microscopy

Specimens stained/labeled with fluorophores which absorb and emit certain wavelengths of light

Electron microscopy

Uses beam of electrons and their wave-like properties to magnify an object’s image. Electron wavelength is much smaller than that of visible light, resulting in high resolution.

Endosymbiosis theory

Eukaryotic cells originated from prokaryotic cells that engulfed other prokaryotic cells which evolved into organelles over time

Endosymbiotic development of eukaryotes

Ancestral prokaryotic cells acquired a heterotrophic prokaryote which becomes the mitochondrion

Endosymbiotic development of photosynthetic eukaryotes

Host cell with mitochondria additionally acquired a photosynthetic prokaryote which becomes the plastid

Similarities of mitochondrion and chloroplasts to bacteria

Size, ribosomes

Mitochondrion and chloroplasts…

Divide by binary fission, have their own circular DNA and ribosomes, have inner membranes similar to those in prokaryotes

Genes and proteins of mitochondria and chloroplasts…

Phylogenetically cluster with alphaproteobacteria and cyanobacteria