Microbio Exam 1

Prokaryotic vs Eukaryotic Cells

Prokaryotic:

• Lack true membrane-delimited nucleus

• Bacteria and Archae

• No organelles (membrane enclosed structures)

Eukaryotes:

• Plants, animals, algae, protozoa, fungi

• Contain organelles

• DNA enclosed in a membrane bound nucleus

• Contain mitochondria and chloroplasts

What are the smallest and simplest “organisms”

Mycoplasmas

• mycoplasma genitalium

  • gram positive bacterium with a 580 kbp genome and 470 defined coding regions

Natural Classification vs Taxonomy

Natural Classification

• Arranges organisms into groups based on shared characteristics

• First classification in 18th century by Linnaeus based on anatomical characteristics

• This approach does not necessarily provide info on evolutionary relatedness

Taxonomy

• Identifies and names different organisms

• Define groups based on relatedness among different organisms

• Morphological Relatedness

• Molecular Relatedness

Binomial Nomenclature

Devised by Carl von Linne (Linnaeus)

• each organism has two names

  • genus name (italicized and capitalized)

  • Species (italicized but not capitalized)

  • e.g. Escherichia coli

• Can be abbreviated after first use (e.g., E. coli)

Prokaryotic Taxonomy

Three separate but interrelated parts

• Classification - arrangement of organisms into groups (taxa)

• Nomenclature - assignment of names to taxa (groups)

  • Identification - determination of taxon to which an isolate belongs

Taxonomic Ranks

From largest (most inclusive) to smallest (specific)

• Domain

• Phylum

• Class

• Order

• Family

• Genus

• Species

Phylogenetic Classification

Phylogeny

• Evolutionary development of a species

Usually based on direct comparison of genetic material and gene products using rRNA nucleotide sequences to assess evolutionary relatedness

Three domains of life

- Archaea

- Bacteria

- Eucarya

Orthologs vs Paralogs

Orthologs have same function and originate from a single ancestral gene in a common ancestor

Paralogs have evolved to have different functions resulting from gene duplication

Which domain has muramic acid in it’s cell walls?

Bacteria

Which domain has ether linked branched aliphatic chains?

Archaea

What evidence was the three domains categorization originally based on?

Small subunit ribosomal rRNA comparison

Selectively permeable barrier, mechanical boundary of cell, nutrient and waste transport, location of many metabolic processes (respiration, photosynthesis), detection of environmental cues for chemotaxis

Plasma Membrane

Buoyancy for floating in aquatic environments

Gas Vacuole

Protein Synthesis

Ribosomes

Storage of carbon, phosphate, and other substances

Inclusion Bodies

Localization of genetic material (DNA)

Nucleoid (Bacteria and Archaea)

In gram negative (thin and pink) bacteria, contains hydrolytic enzymes and binding proteins for nutrient processing and uptake; in gram positive (thick and purple) bacteria and archaeal cells, may be smaller or absent

Periplasmic Space

Provides shape and protection from osmotic stress

Cell Wall

Resistance to phagocytosis, adherence to surfaces; rare in archaea

Capsules and slime layers

Attachment to surfaces, bacterial conjugation and transformation, twitching and gliding motility

Fimbriae and Pili

Swimming motility

Flagella

Survival under harsh environmental conditions; only observed in bacteria

Endospore