Intro to Bacteria Flashcards
List some parts of a bacterium
Capsule, cell wall, cytoplasmic/inner/plasma membrane, ribosomes, single chromosome (no nucleus), flagellum, fimbriae
explain the cytoplasmic/plasma membrane of bacterial cells
thin, elastic and semi-permeable membrane around bacterial cell contents
What lies ouside the cytoplasmic membrane of bacterial cells
the cell wall - rigid, giving cell strength and shape but is permeable
What is the outer membrane a component of
the gram negative cell wall
Gram positive bacteria
bacteria that have a thick peptidoglycan cell wall, and no outer membrane
gram negative bacteria
Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane. Gram-negative bacteria are typically more resistant to antibiotics than Gram-positive bacteria
What colours do gram +ve and gram -ve bacteria stain
Gram positive - purple
Gram negagtive - pink (red)
why are mycobacteria not reliably stained by gram stain
due to the large lipid content in the cell wall
shape of cocci under microscope
spherical
shape of bacilli under microscope
rod shaped
How can bacteria appear under a microscope
may be spiral or corkscrew, spherical or rod shaped, can exist as single cells, chains or clusters
Explain the bacterial cytoplasmic membrane in more detail
- Composed of phospholipids and proteins
- Allows the passage of water and uncharged small molecules but otherwise forms a barrier
- Proteins oif membrane have number of functions:
- transport systems for specific nutrients and ions
- as enzymes involved in processes such as energy generation, cell wall synthesis and DNA replication
- Sensing proteins that measure concentrations of molecules in the environment
Explain the bacterial cell wall
- made of peptidoglycan: N-acetylglucosamine acid and Nacetylmuramic acid molecules linked alternately in a chain, with short peptides forming cross-links
- thick, strong and relatively rigidmaintains shape
- several antibiotics interfere with the construction of cell wall peptidoglycan -e.g. penicillan?
what happens if the cell wall is weakened or ruptured?
osmosis means the cell will swell and burst -termed lysis
role of cell wall in cell division
The cell wall plays an important part in cell division ie cross-walls form prior to separating into 2 daughter cells
Describe the Lipopolysaccharide (LPS) outer membrane
Where is it present, function, structure…
- only present in Gram negative bacteria
- protects peptidoglycan from bile salts (in the gut), also from lysozyme
- blocks many antibiotics getting into the cell
- lipid A (within LPS) forms endotoxin, which, when released into the bloodstream (when multiplying or when lysed), may give rise to endotoxic shock -fever and low blood pressure
WHat is the bacterial capsule
the polysachharide layer found outside the cell wall
How do bacteria replicate and how does genertic variation arise
- replicate by binary fission (identical progeny)
- Genetic variation by: spontaneous mutation, transfer of DNA
Bacterial conjugation
Conjugation is the process by which one bacterium transfers genetic material to another through direct contact. During conjugation, one bacterium serves as the donor of the genetic material, and the other serves as the recipient.
What are bacteriophages
viruses that can infact bacteria
Bacterial Ribosomes
- Consist of RNA and associated proteins
- function is to synthesise proteins
- divided into subunits - measurement is by the Svedberg unit, a measure of sedimentation rather than size
- bacteria have a 70S ribosomes, with large (50S) and small (30S) subunits. The small 30S subunit has itself a subunit, called 16S.
dont think you need to know the non-bold bits :)
How can we detect and culture:
* individual bacteria
* colonies of individual bacteria
- individual bacteria: can only be seen with a microscope, use a stain (e.g. gram/flourescent dyes)
- colonies of individual bacteria: cultured on a solid medium (agar), can be see by eye
How can we classify bacteria
Phenotypically (observable physiocal properties) or genotypically (relating to DNA)
Give examples of phenotypic bacterial classification
- gram stain
- growth requirements eg aerobic, anaerobic, microaerophilic
- serologic
- mass spectrometry (protein profiling)
Give examples of genotypic bacterial classification
- ribosomal RNA sequence analysis
- whole genome sequencing
bacterial nomenclature
- name based on genus and species
- strains of a species have similar characteristics
- DNA typing techniques is used to identify strains
Flagella
Flagellum is primarily a motility organelle that enables movement and chemotaxis. Bacteria can have one flagellum or several, and they can be either polar (one or several flagella at one spot) or peritrichous (several flagella all over the bacterium).
Fimbriae
Fimbriae are long filamentous polymeric protein structures located at the surface of bacterial cells. They enable the bacteria to bind to specific receptor structures and thereby to colonise specific surfaces - ADHESION AT EPITHELIAL SURFACES
Bacterial spores
A spore is a cell that certain fungi, plants (moss, ferns), and bacteria produce. Spores are involved in reproduction. Certain bacteria make spores as a way to defend themselves. Spores have thick walls
Penicillin binding protein
Penicillin-binding proteins are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria
