Microbiology 2: Bacterial Structure and Growth Flashcards Preview

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Flashcards in Microbiology 2: Bacterial Structure and Growth Deck (20):

What is flagella?

Fine processes made out of a protein called flagellin that are responsible for motility for the bacteria


What are the distinguishing features of Fungi?

• Mushrooms, moulds and yeasts.
Mushrooms produce toxins.
Moulds have filamentous structures called hyphae.
Yeasts are just single cellular. Yeasts reproduce by budding, other fungi reproduce by spore formation
• Fungi can be identified by their spores


How do bacteria move?

By using Flagella


There are four oxygen requirements of bacteria. What are they?

o Aerobic – need oxygen
o Anaerobic – cannot grow in the presence of oxygen
o Facultative – can grow with or without oxygen
o Microaerophilic – require a low concentration of oxygen


What is the composition of Capsules?

Composed of complex polysaccharides and have a mucoid appearance


Often found in gram positive rods, what allows bacteria to survive for longer periods of time under adverse conditions?

Bacterial spores


Is bacterial growth exponential?



How does binary fission work?

1. Cell elongates and nuclear material in cell doubles. DNA attaches to cell membrane
2. Cell wall and plasma membrane begin to divide
3. The cells are still joined at the centre by a narrow neck
4. DNA scattered in central region of each cell


What are pili/fimbrae and what are their purposes?

Pili/fimbrae are filaments that come from the outside surface of bacterial cells, and are most important for adhesion to host cells and attach to other surfaces I'm order to survive

They are especially important in the gut or kidneys where they are likely to be swept away


What are endospores?

A metabolically inactive spore that can withstand much tougher conditions than any vegetative cell, that allows the to survive when they environment is not suitable.


Do spores germinate and go back into a vegetative state after being dormant (if the conditions are right)?



What are the sites for bacterial infections?

Lung – pneumonia – streptococcus pneumonia

Skin – impetigo – streptococcus pyogenes

Nervous system – meningitis – haemophilus influenza

Urinary tract - pyelonephritis- E.coli

Genital tract – gonorrhoea – neisseria gonorhoeae

Stomach – peptic ulcer disease – heliobacter pylori

Intestine – typhoid fever – salmonella typhi


What are the two media for bacteria growth?

1. Liquid medium:
o useful for increasing

2. numbers of bacteria
Solid medium (solidified liquid medium):
o useful for isolating single colonies and facilitates identification of pathogens
 -colonies arise from a single bacterium
 -different size, shape, colour, texture can help identify bacteria
o agar is added to solidify the media (melts 100°, sets at 44°)


The bacterial growth curve has four distinct phases. What are they?

• Lag phase – first few hours of growth. Bacteria are adapting to the new environment – making proteins that will allow it to thrive

• Log phase – active stage of growth. Rapid reproduction. This is the point where symptoms usually develop

• Stationary phase – population less vigorous. Reproductive and death rates become equal (e.g. due to lack of nutrients, toxic metabolites or host immune response)

• Death or decline phase – environment becomes too adverse and numbers start to decrease. Death rate exceeds reproductive rate


What is motility important for?

Colonisation, as well as for finding nutrients in areas where growth is favoured


What are the distinguishing features of Archaeaic microbes?

• Prokaryotic
• Resemble bacteria

o Cell walls do not contain peptidoglycan
o Adapted to survive under extreme conditions
o Cell membranes contain different lipid composition
o Unique nucleotide sequences in the RNA of their ribosomes
• Not established as a cause of human disease


How do bacteria grow?

Binary fission


What are the distinguishing features of protozoa?

• Largest of all microorganisms
• No chlorophyll
• Single cellular and multicellular forms
• Obtain nutrients by engulfing food particles, phagocytosis (including bacteria)
• Reproduce asexually
• malaria – plasmodium species (transmitted by mosquitoes)
• giardiasis – giardia lamblia (water borne)


What are the pH requirements of bacteria?

o Most bacteria grow best around pH 7 (for reference human blood and tissue has a pH 7.2-7.4)

o Most bacteria do not grow well in acidic conditions, except for acidophiles (heliobacter pylori can grow in pH 2 stomach acid)


What are bacteria optimal growth temperatures?

1. Psychrophiles (0-20)
2. Mesophiles (20-40)
-Main group associated with human disease
3. Thermophiles (40-90)