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Microbiology > Bacteria > Flashcards

Bacteria Flashcards

1
Q

Bacteria are ____karyotic organisms. I.E they _____

A

Bacteria are prokaryotic organisms. I.E they lack defined nucleus

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2
Q

What are the (5) integral structural components of bacteria?

A
  1. A genome (DNA)
  2. A cell membrane
  3. A cell wall
  4. Ribosomes
  5. Periplasmic space
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3
Q

Describe the bacterial genome with regards to it’s structure and it’s position within the cell.

A

The bacterial genome consists of circular chromosomes made from dsDNA that are free floating within the nucleoid. As well as plasmids (smaller pieces of dsDNA)

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4
Q

Bacteria can be classified as “Gram positive” or “Gram negative” depending on …..

A

Whether they contain a thick layer of peptidoglycan (gram postive) or a thin layer (gram negative) of peptidoglycan in their cell wall.

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5
Q

The cell wall of Gram postive bacteria contain ___ acids which Gram negative bacteria lack. They give the cell wall a ___ charge and are thought to play a role in ____.

A

Teichoic acids are found in the cell walls of Gram positive bacteria. They give the cell wall a slight negative charge and are thought to play a role in adhesion to tissue surfaces.

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6
Q

The cell walls of Gram negative bacteria contain the component ___ which Gram positve bacteria lack.

A

Lipopolysacharides (LPS). They are located mainly on the outer surfaces of the outer membrane.

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7
Q

Gram ____ bacteria contain a large periplasmic space enclosed with an outer membrane. Whilst Gram ___ either do not or contain a very small periplasmic space.

A

Gram negative bacteria contain a large periplasmic space enclosed with an outer membrane. Whilst Gram postive either do not or contain a very small periplasmic space.

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8
Q

A procedure to determine whether bacteria are either gram negative or gram postive is called ____.
Describe the steps to this procedure.

A

Gram staining procedure (or just a Gram stain)

  1. Application of the purple / crystal violet stain
  2. Application of iodine as a mordent
  3. Alcohol wash (decolourization)
  4. Application of the counter stain (pink / red dye)
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9
Q
  1. Which type of bacteria retains the purple dye stain?

2. Which loses the purple dye stain but retains the pink counterstain?

A
  1. Gram positive

2. Gram negative

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10
Q

Why might a gram positive bacteria fail to retain the purple dye during a Gram staing procedure?

A

If the cell wall is damaged during the procedure either by exposure to too much heat or too long in the alcohol wash stage. Or if the culture is old.

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11
Q

Why might a Gram negative bacteria appear to retain the purple dye?

A

If the bacterial smear is too thick the gram negative bacteria may appear to be gram positive.

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12
Q

What are two ways to try and avoid false results when carrying out a gram stain?

A
  1. Use a fresh sample of the bacteria
  2. Always try the procedure out first on bacteria that you know are gram positve or gram negative to ensure correct technique.
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13
Q

With regards to bacterial structure there are 7 key organelles we have to think about . Name the 7 organelles.

A
  1. Pili(fimbriae) 2. Flagella (flagellum)
  2. Ribosomes 4. Chromosomes
  3. Capsule 6. Inclusion bodies
  4. Endospores
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14
Q

Briefly describe the role of

  1. Ribosomes
  2. Inclusion bodies
  3. Endospores
A
  1. The sight of translation during protein synthesis
  2. Bodies of reserve material within the cell
  3. Highly resistant structure that can protect bacteria in hostile enviroments such as high temp, irradiation etc
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15
Q

The role of (1) flagella (2) F pilli (b) fimbriae (3) capusle

A
  1. Allows the cell to be motile
  2. F Pili are involved in bringing two bacteria together during conjugation
    (b) Fimbriae are involved with the adhesion of bacteria onto tissue surfaces
  3. Protects against phagocytosis
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16
Q

What shapes , respectively, do the following denote ?

  1. Spirochetes
  2. Bacilli
  3. Cocci
  4. Vibrio
A
  1. Thin flexible spiral
  2. Rod-shaped
  3. Sphere shaped
  4. Curved of comma shaped
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17
Q

Staphlyococci would indicate ______
Streptococci would indicate ______
Pneumococci would indicate ______

A

Clustered cocci
A chain of cocci
A pair of cocci

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18
Q

What are the functions of the outer membrane?

A

Forms the outer limit of the periplasmic space and provides a permeability barrier. Receptor for F pilus (conjugation). Helps evade phagocytosis. Allows passage of nutrients through porins.

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19
Q

Flagellum distribution can be four types, desribe them.

  1. Monotrichous
  2. Amphitrichous
  3. Lophotrichous
  4. Peritrichous
A
  1. Monotrichous - 1 flagellum located at 1 pole of the cell
  2. Amphitrichous - 1 flagellum at each pole of the cell
  3. Lophotrichous - A short cluster of flagellum at one or both poles of the cell
  4. Peritrichous- flagella distributed over the whole surface of the cell
20
Q

WIth regards to bacteria, what is the meaning of the term binary fission.

A

Binary fission is the asexual process of cell division to produce two identical daughter cells.

21
Q

In an early stage of binary fission (once or whilst the chromsome has been duplicated) the parent cell prepares for cell division by ____

A

The parent cell prepares for cell division by enlarging its cell wall, cell membrane and overall volume.

22
Q

In binary fission once the parent cell has elongated what is the next stage?

A

The plasma membrane pinches inwards at the centre of the cell. When the nuclear material has been evenly distributed the cell wall thickens and grows inward seperating the divding cell in to two daughter cells.

23
Q

Name the 4 stages of a a bacterial growth curve.

A
  1. Lag phase
  2. Log phase
  3. Stationary phase
  4. Death Phase
24
Q

Describe and explain the Lag phase of a bacterial growth curve.

A

Description - No change in cell number.
Explanation - The bacteria is adapting to a new enviroment - altering gene expression to produce required proteins and repairing damage.

25
Q

Describe and explain the Log phase of a bacterial growth curve.

A

Description - During the log / exponential phase bacteria population numbers double at regular intervals.
Explaination - Bacteria have adapted to the new enviroment and growth is efficient. There are an excess of nutrients available and an exponential population growth.

26
Q

Describe and explain the Stationary phase of a bacterial growth curve.

A

Description - The rate of cell death = the rate of cell growth.Cell number remains stable.
Explaination - Nutrients and space are beginning to run out. As the rate of cell death increases and the rate of cell growth decreases there is no net gain in population growth.

27
Q

Describe and explain the Death phase of a bacterial growth curve.

A

Description - Rate of cell death > rate of cell growth. Population decreases.
Explanation - Cells are beginning to die due to lack of nutrients and O2, and the build up of toxins.

28
Q

Name and describe 3 consequences if the temperature exceeds an organisms optimal temp range.

A
  1. Enzymes will become denatured and enzyme activity will reduce.
  2. Hydrogen bonds between DNA nucleotides will break
  3. The membrane will become too fluid and no longer act as an efficient permeability barrier.
29
Q
  1. What is the optimum temperature range for mesophiles?

2. Which of psychrophiles and thermophiles could be described as cold-loving?

A
  1. 20C - 45C

2. Psychrophiles

30
Q

Give the term for the following -

  1. “Acid-loving” organisms
  2. Organisms that grow best at neutral pH
  3. “Alkali-loving” organisms
A
  1. Acidophiles
  2. Neutrophiles
  3. Alkalophiles
31
Q

Explain the relationship between oxygen and the following -

  1. Aerobes
  2. Faculative aerobes
  3. Anaerobes
  4. Microaerophiles
A
  1. Aerobes - require oxygen for respiration
  2. Faculative aerobes - can grow in the presence or absence of oxygen
  3. Anaerobes - need an oxygen free enviroment
  4. Microaerophiles - Use low concentration of oxygen in respiration but find high concentration oxygen toxic.
32
Q

What does bacteriostatic refer to?

A

An agent which prevents the growth of bacteria without necessary killing them

33
Q

What does bacteriocidal refer to?

A

An agent which kills existing bacteria and prevents the growth of new bacteria.

34
Q

Describe the 4 characteristics which are often observed when bacteria are grown in a closed system under sub-optimal conditions.

A
  1. Decreased respiration (therefore decreased energy for growth and division.
  2. Maximum population size would be less and growth rate would be less
  3. Death phase would begin earlier
  4. Endospore formation would occur if possible to allow bacteria to survive.
35
Q

Name and describe a gram positive bacteria

A

Bacillus subtilis is a gram postive bacteria which inhabits soil. Bacillus subtilis can be found colonising the roots of plants (in the rhizosphere) whom it forms a mutually beneficial (symbiotic) relationship with. Bacillus subtilis is a phosphate solubilising bacteria and this can improve the nutrional content of the soil for the plant.

36
Q

Name and drescribe a gram negative bacteria

A

Vibrio cholerae is a gram negative bacteria which is found in water and is the causative agent of cholera. The bacteria can enter the intestinal tract via contaminated water or food. It is susceptible to stomach acid but if enough bacteria is ingested it can colonise the intestine. The bacteria secretes an enterotoxin which stimulates a massive loss of fluid in humans.

37
Q

Name and describe a bacteria found in water

A

Vibrio cholerae is a gram negative bacteria which is found in water and is the causative agent of cholera. The bacteria can enter the intestinal tract via contaminated water or food. It is susceptible to stomach acid but if enough bacteria is ingested it can colonise the intestine. The bacteria secretes an enterotoxin which stimulates a massive loss of fluid in humans.

38
Q

Name and describe a bacteria found in soil

A

Bacillus subtilis is a gram postive bacteria which inhabits soil. Bacillus subtilis can be found colonising the roots of plants (in the rhizosphere) whom it forms a mutually beneficial relationship with. Bacillus subtilis is a phosphate solubilising bacteria and this can improve the nutrional content of the soil for the plant.

39
Q

Name and describe a bacteria found in the human body

A

E. coli is a gram negative rod shaped bacteria that inhabits the human body. E. coli can be a directly beneficial bacteria as it prevents the overgrowth of harmful bacteria in the body via microbial antagonism. E. coli produce bacteriocins, chemicals that inhibit the growth of harmful bacteria in the gut. E. coli also produces vitamin K.

40
Q

Name and describe a bacteria found on surfaces

A

Serratia marcescens is a gram negative rod shaped bacteria that can inhabit damp surfaces. It is a faculative anaerobe and an opportunistic pathogen. Serratia marcescens can form a biofilm on surfaces, making it more resistant to treatment and disinfectant.

41
Q

Name and describe a bacteria which can create a biofilm

A

Serratia marcescens is a gram negative rod shaped bacteria that can inhabit damp surfaces. It is a faculative anaerobe and an opportunistic pathogen. Serratia marcescens can form a biofilm on surfaces, making it more resistant to treatment and disinfectant.

42
Q

Name and describe a beneficial bacteria

A

E. coli (Escherichia Coli) is a gram negative rod shaped bacteria that inhabits the human body. E. coli can be a directly beneficial bacteria as it prevents the overgrowth of harmful bacteria in the body via microbial antagonism. E. coli produce bacteriocins, chemicals that inhibit the growth of harmful bacteria in the gut. E. coli also produces vitamin K.

43
Q

Name and describe an indirectly beneficial bacteria

A

Alcanivorax borkumensis is a gram negative bacteria found in water (hot springs). It is a bioremediator of oil spills as it causes the hydrocarbons to oxygenase.

44
Q

Name and describe a harmful bacteria

A

Vibrio cholerae is a gram negative bacteria which is found in water and is the causative agent of cholera. The bacteria can enter the intestinal tract via contaminated water or food. It is susceptible to stomach acid but if enough bacteria is ingested it can colonise the intestine. The bacteria secretes an enterotoxin which stimulates a massive loss of fluid in humans.

45
Q

Name and describe an indirectly harmful bacteria

A

Clostridium chauvoei is a gram positive bacteria which is found in soil. In sheep and cattle, clostridium chauveoi causes the fatal disease black leg. Therefore it results in the loss of livestock and is detrimental to the food production industry.

Microbiology (4 decks)

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