Bacteria Lectures 1-3 Flashcards
Understand this Shiz
Key distinguishing features of Prokaryotes from Eukaryotes?I
Prokaryotes:
- not compartmentalised (no ER, Mitochondria, lysosome)
- ATP made in plasma membrane via oxidative phosp.
70s ribosomal unit as opposed to the 80s in eukaryotes
Steps of how to Do the Gram Stain
1: Crystal Violet is the primary stain
2: Iodine Solution/ Gram’s Iodine (fixes Violet in cell wall)
3: Decolouriser is applied e.g ethanol
4: Safranin (Counter stain)
How does Gram Stain work??
Gram +ve have thicker peptidoglycan layer (and lower lipid content) and can retain the crystal Violet stain
Gram -ve lose the crystal Violet stain and are instead stained by safranin
How does the Decolouriser work in Gram negative staining
It dissolves the lipid layer from the Gram -ve cells. The removal of lipid layer enhances the leaching of the primary strain from the cells into the surrounding solvent
How does the Decolouriser work on Gram +ve staining
The Decolouriser closes the pores as the cell wall shrinks during dehydration. As a result the diffusion of the violet-iodine complex out of cell is blocked + bacteria remains stained
What does prolonged exposure to Decolourising agent cause?
it will remove stains from both types of bacteria
Bacteria that lose the stain easily appear to be a mixture of gram +ve and gram -ve. This is known as
Gram Variable
what shape do Cocci appear as
Spherical
what shape do bacilli appear as
Rod shape
What shape do Spirillium appear as
Spiral
what shape do Vibric appear as?
curved rod shaped
What additional function do Prokaryotic cells have on their plasma membrane to Eukaryotes
Electron Transport and the Phosphorylation of ADP
3 Key features of the bacteria cytoplasmic matrix
1: Nucleoid - consists of supercoiled
2: Plasmid - Extra Chromosomal DNA often coding for antibiotic chromosome
3: Inclusion bodies - granules of organic/inorganic and may be bound by protein or lipid membranes
Features of a bacterial gram +ve envelope
Cell wall consists of many layers of peptigoglycan formed by alternating units of NAG and NAM cross-linked by short peptides.
NAG and NAM arrangements gives a strong and rigid but semi-permeable structure
State the 3 different Symbiotic Relationships with Microbes and Humans. State examples
Mutualism - e.g Lactobacillus acidophilus
Commensialism - e.g Escherichia Coli
Parasitism - e.g Helicobacter Pylori
What does NAG and NAM stand for
NAG = N-acetylglucosamine and NAM = N-acetylmuramic acid
Features of a bacterial gram -ve envelope
The most inner layer is composed of a phospholipid layer. Outer membrane is made up of lipopolysaccharide (LPS).
In between membrane = periplasmic space
On a gram -ve envelope, what does the periplasmic space consist of
Peptidoglycan layer and Periphrastic proteins
Tell me more about Lipopolysaccharide
Makes up the outer membrane of gram -ve bacteria and is an endotoxin. On destruction of the cell, it is released into the environment. This can be toxic to humans.
What is Acid Fastness?
A physical property that relates to their resistance to decolourisation by acids in the staining procedure
Give an example of an acid fast bacteria. What happens to it in acid-fast testing?
mycobacterium tuberculosis - It is stained red after the decolourisation step during the acid fast staining procedure
Characteristics of a acid-fast bacterium
cell walls contain large amounts of lipid substance (mycolic acid) resulting in a very hydrophobic cell wall. This allows for survival within Macrophages and intrinsic resistance to antimicrobials
External Components of all Bacterium
All bacterium secrete a form of glycocalyx. Having this layer aids adhesion to environment, and allows host to form a colony or bio-film formation. This helps inhibit opsonisation
If glycocalyx is tighly bound to the cell, the bacterium is referred to as..
A Capsule
If glycocalyx is loosely bound to the bacterium, it is referred to as…
The Slime layer
What is Opsonisation
Identification and subsequent destruction by a phagocyte
Describe the bacterial flagella
Long protein filament extending from cell envelope. The molecular motor is driven by Proton Motive Force.
Describe the Pilli and state its role on a bacterium
Hair-like projections from the bacterium. Involved in conjugation & Plasmid transfer. Also involved in attachment to host epithelium.
What can happen under environmental stress from bacteria, that allows them to resist destruction?
- Formation of endospores (most commonly by genera of bacillus clostridium) They are highly resistant dehydrated structures containing bacterial genome.
- Resistant to high temp, UV, Chemical and Enzymatic damage.
What are Nitrogens used for biologically and give examples of nitrogen containing compounds
e.g NH4+ and NO3-. Nitrogen is a constituent of amino acids, nucleotide, phospholipids, cell wall component etc.
What is Sulphur used for biologically and give examples of Sulphur containing compounds
e.g SH. Required for disulfide brdges, cysteine + Methionine + B Vitamins
What is Carbon used for biologically and give examples of Carbon containing compounds
e.g CO2, CHO’s, Oil, Plastics. Carbon is the backbone for all functional biological molecules, sources.
I know it’s simple but whats oxygen for
required for synthesis of organic molecules and as a terminal electron acceptor of electron transport in anaerobes
Define Commensalism
Bacterium uses larger organism as its physical environment, acquiring nutrients, but not directly from host organism
Define Mutualism and give a practical example where this occurs
Bacterium and larger organism have a mutually beneficial relationship e.g Normal gut flora digesting complex carbohydrates
Define Parasitism
Bacterium lives at the expense of the larger organism
An Anaerobe that is completely dependent on oxygen for growth is called… and an example is..?
Obligate Aerobe, e.g Mycobacterium Tuberculosis, lives in the lungs
A Bacterium that does not require oxygen for growth but grows better in its presence is called.. e.g..?
Facultative Anaerobe e.g Escherichia Coli
A Bacterium that grows equally well in the presence & Absence of oxygen is called… e.g?
Aerotolerant e.g Streptococcus Pyogenes
A Bacterium that dies in the presence of oxygen is called.. eg?
Obligate Anaerobe e.g Clostridium Spp - These produce spores that can exist outside the body. Faecal Oral contact allows spores to enter GI then germinate
A Bacterium that requires 2-10% of oxygen and is damaged by atmospheric oxygen is called.. eg?
Microaerophile e.g Treponema Pallidum
What is a primary metabolite and provide examples
Primary metabolites are produced during the log phase of growth. It is essential for cells growth, e.g Amino Acids, Lipids, etc
What is a secondary metabolite and provide examples
Secondary metabolites are produced at the onset of the stationary phase or as a result of quorum sensing; e.g Alkaloids, Antibioitics, Toxins, Pheromones etc.
Reasons for high bacterial abundance
- divide rapidly
- diverse set of species physiology
- aerobic or anaerobic bacteria exist
what is sterilisation of microbes?
The complete removal of microbes or damaging microbes such that all our killed. It does not use antimicrobial agents. e,g
- Heat
- Ionising
- Filter sterilisation
