bacteria and archaea

Common features of Prokaryotic and Eukaryotic Cells

DNA and chromosomes, Cell membrane, Cytoplasm, Ribosomes, Cytoskeleton.

Bacteria characteristics: Chromosome

One circular chromosome, not membrane bound.

Bacteria characteristics: Histones

No histones.

Bacteria characteristics: Organelles

No organelles (except ribosomes).

Major component of Bacterial cell walls

Peptidoglycan cell walls.

Bacteria reproduction method

Binary fission.

Average size of bacteria

0.2 - 1.0 μm  2 - 8 μm.

Three basic shapes of bacteria

Bacillus, Coccus, Spirals.

External Structure: Glycocalyx

External surface layer composed of sticky polysaccharides or polypeptides.

Glycocalyx types

Capsule (organized and firmly attached) and Slime layer (unorganized and loosely attached).

Function of Fimbriae

Allow attachment and adhesion to epithelial cells.

Function of Pili

Used to transfer DNA between cells (conjugation).

Function of Nanotubes

Used as channels to transfer amino acids or to harvest energy.

Contents of Bacterial Cell Wall

Consists of peptidoglycan, composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).

Gram Positive Cell Wall characteristics

Thick layer of peptidoglycan with negatively charged teichoic acids.

Gram Negative Cell Wall characteristics

Thin peptidoglycan layer with an outer membrane.

Gram Stain Mechanism for Gram-Positive

Crystal violet crystals do not leave due to dehydrated peptidoglycan.

Gram Stain Mechanism for Gram-Negative

Alcohol dissolves outer membrane and CV-I washes out.

Mycoplasmas

Bacteria with no cell wall; stabilized by sterols in the cell membrane.

Acid-fast Cell Walls

Found in Mycobacterium and Nocardia; have a waxy lipid layer that doesn't stain well.

Damage to Cell Wall

Lysozyme digests disaccharides in peptidoglycan; penicillin inhibits peptide bridges.

Bergey’s Manual of Systematic Bacteriology

Comprehensive view of bacterial and archaeal relatedness based on rRNA sequencing.

Taxonomic Scheme: Gracilicutes

Gram-negative with thin cell walls.

Taxonomic Scheme: Firmicutes

Gram-positive with thick, strong cell walls.

Taxonomic Scheme: Tenericutes

Lack a cell wall and are soft.

Taxonomic Scheme: Mendosicutes

Archaea with unusual cell walls.

Bacterial species definition

A collection of bacterial cells sharing an overall similar pattern of traits.

Criteria for bacterial species

Should share at least 95% of their genes as matches.

Subspecies definition

Bacteria of the same species that have differing characteristics.