Lecture 1: Introduction and microbial cell biology
Microorganisms: Organisms (microbes) that are too small to be seen with the unaided human
eye.
Microbial community: Two or more populations of microbes that coexist and interact in a
habitat.
Cytoplasmic membrane: Semipermeable membrane which separates the cell's interior (the
cytoplasm) from the outside environment.
Ribosome: A cytoplasmic particle that is composed of rRNA and proteins. It is used in the cell to
translate mRNA into proteins.
Cell wall: Rigid layer on the outside of the cytoplasmic membrane which ensures structural
strength. Cell walls are not present in animal cells, but are present in plant cells, bacteria and
fungi.
Nucleoid: genetic material of a prokaryote that is in the cytosol as circular chromosomes
Prokaryotes:
- No nucleus; only nucleoids
- No traditional organelles; Moreso structures with functions
Eukaryotes:
- Nucleus; Genetic material in linear chromosomes
- Membrane enclosed organelles; Mitochondria, Rough ER/Smooth ER, etc.
Metabolism: All biochemical reactions going on within a cell
Motility: Movement of cells by some form of self-propulsion
Basic functions of a microbial cell:
- Metabolizing, Evolving, Growing and Maintaining structure
- Extra properties found in some microbial cells: Differentiation, Communication,
Exchange of genetic information and Motility
Morphology: Physical appearance of a cell determined by its cells shape (i.e. cone, sphere, rod,
etc.).
,Types of solutions:
Isotonic: Solution that has the same concentration of dissolved substances as the concentration
within the cell. Nothing happens to the cell.
Hypertonic: Solution has a higher concentration of dissolved substances as the concentration
within the cell. The cell will shrink due to water loss because of osmosis.
Hypotonic: Solution has a lower concentration of dissolved substances as the concentration
within the cell. The cell will eventually burst (cell lysis) due to water influx because of osmosis.
Phospholipid bilayer: A double layer of phospholipids that make up the cell membrane. It
consists of hydrophobic tails (made from fatty acids) and a hydrophilic head (glycerophosphate
+ a side chain of sugars)
Transmembrane protein: A protein that is integrated into the cell membrane.
Peripheral membrane protein: A protein that is attached to the membrane protein.
Gram-positive vs. Gram negative cell walls: Both cell walls consist of a polysaccharide called
Peptidoglycan. The layers in which peptidoglycan is used do differ between gram positive and
gram-negative cell walls. Gram-positive cell walls mostly consist of this peptidoglycan, up to
90%. Gram negative cell walls contain way less peptidoglycan and contain an additional outer
membrane made of lipopolysaccharides.
Peptidoglycan: A polysaccharide composed of N-Acetylglucosamines and N-Acetylmuramic
acids that are arranged in adjacent layers cross linked by short peptides.
, Glycan tetrapeptides: Short peptide side chains consisting of L-alanine, D-alanine, D-glutamic
acid and L-lysine. D-amino acids are found in peptidoglycans and L-amino acids are found in
proteins.
Teichoic acid: phosphorylated polyalcohol (B-1,4-linked) in the cell wall of a gram-positive
bacteria.
Peptidoglycan biosynthesis is a property of microbes that is often targeted for destroying the
cell. For instance: Penicillin inhibits transpeptidase, meaning the linking peptide bonds withing
the peptidoglycan can't be made, causing the peptidoglycan to fall apart. And lysozymes,
proteins found in saliva, hydrolyze part of the peptidoglycan, compromising its structure.
Lipopolysaccharides (LPS): combination of lipids with polysaccharides and proteins that forms a
major portion of the outer membrane found in gram-negative bacteria.
S-Layer: An additional layer of proteins found in almost all bacteria and archaea that functions
as a protective coat, molecular sieves (pores), surface recognition and cell adhesion.
Microorganisms: Organisms (microbes) that are too small to be seen with the unaided human
eye.
Microbial community: Two or more populations of microbes that coexist and interact in a
habitat.
Cytoplasmic membrane: Semipermeable membrane which separates the cell's interior (the
cytoplasm) from the outside environment.
Ribosome: A cytoplasmic particle that is composed of rRNA and proteins. It is used in the cell to
translate mRNA into proteins.
Cell wall: Rigid layer on the outside of the cytoplasmic membrane which ensures structural
strength. Cell walls are not present in animal cells, but are present in plant cells, bacteria and
fungi.
Nucleoid: genetic material of a prokaryote that is in the cytosol as circular chromosomes
Prokaryotes:
- No nucleus; only nucleoids
- No traditional organelles; Moreso structures with functions
Eukaryotes:
- Nucleus; Genetic material in linear chromosomes
- Membrane enclosed organelles; Mitochondria, Rough ER/Smooth ER, etc.
Metabolism: All biochemical reactions going on within a cell
Motility: Movement of cells by some form of self-propulsion
Basic functions of a microbial cell:
- Metabolizing, Evolving, Growing and Maintaining structure
- Extra properties found in some microbial cells: Differentiation, Communication,
Exchange of genetic information and Motility
Morphology: Physical appearance of a cell determined by its cells shape (i.e. cone, sphere, rod,
etc.).
,Types of solutions:
Isotonic: Solution that has the same concentration of dissolved substances as the concentration
within the cell. Nothing happens to the cell.
Hypertonic: Solution has a higher concentration of dissolved substances as the concentration
within the cell. The cell will shrink due to water loss because of osmosis.
Hypotonic: Solution has a lower concentration of dissolved substances as the concentration
within the cell. The cell will eventually burst (cell lysis) due to water influx because of osmosis.
Phospholipid bilayer: A double layer of phospholipids that make up the cell membrane. It
consists of hydrophobic tails (made from fatty acids) and a hydrophilic head (glycerophosphate
+ a side chain of sugars)
Transmembrane protein: A protein that is integrated into the cell membrane.
Peripheral membrane protein: A protein that is attached to the membrane protein.
Gram-positive vs. Gram negative cell walls: Both cell walls consist of a polysaccharide called
Peptidoglycan. The layers in which peptidoglycan is used do differ between gram positive and
gram-negative cell walls. Gram-positive cell walls mostly consist of this peptidoglycan, up to
90%. Gram negative cell walls contain way less peptidoglycan and contain an additional outer
membrane made of lipopolysaccharides.
Peptidoglycan: A polysaccharide composed of N-Acetylglucosamines and N-Acetylmuramic
acids that are arranged in adjacent layers cross linked by short peptides.
, Glycan tetrapeptides: Short peptide side chains consisting of L-alanine, D-alanine, D-glutamic
acid and L-lysine. D-amino acids are found in peptidoglycans and L-amino acids are found in
proteins.
Teichoic acid: phosphorylated polyalcohol (B-1,4-linked) in the cell wall of a gram-positive
bacteria.
Peptidoglycan biosynthesis is a property of microbes that is often targeted for destroying the
cell. For instance: Penicillin inhibits transpeptidase, meaning the linking peptide bonds withing
the peptidoglycan can't be made, causing the peptidoglycan to fall apart. And lysozymes,
proteins found in saliva, hydrolyze part of the peptidoglycan, compromising its structure.
Lipopolysaccharides (LPS): combination of lipids with polysaccharides and proteins that forms a
major portion of the outer membrane found in gram-negative bacteria.
S-Layer: An additional layer of proteins found in almost all bacteria and archaea that functions
as a protective coat, molecular sieves (pores), surface recognition and cell adhesion.
