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Y2S1_FST2110 - Microbiology and fermentation > Lect 1 : Microorganisms in foods > Flashcards

Lect 1 : Microorganisms in foods Flashcards

- Recognise bacteria, yeast, mold and virus as sources of MO in foods. Know how they reproduce, morphology etc - Recognise the sources of MOs in foods

1
Q

What is a prokaryote?

A

A microscopic single-celled organism which does not have a distinct MEMBRANE-BOUND nucleus and (other specialised) organelles

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2
Q

What is a eukaryote?

A

An organism consisting of a cell / cells in which genetic material is DNA in the form of chromosomes, contained within a distinct nucleus

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3
Q

What are microorganisms?

A

Microorganisms are small organisms that cannot be seen with the naked eye.

micro : small
organisms : living things

They are also known as microbes

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4
Q

List the 5 types of microorganisms (MOs) and state if they are prokaryotes/eukaryotes/NA (if NA, what category do they belong to?)

A
  1. Bacteria - prokaryotes
  2. Yeast - eukaryote
  3. Mold / mould : eukaryote
  4. Protozoa : eukaryotes
  5. Virus : non-living things
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5
Q

What is protozoa?

A

Single-celled animals (prokaryotes)

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6
Q

Which is the most important class of microbes?

A

Bacteria

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7
Q

Morphology : name the different shapes of bacteria cells (give singular and plural forms)

A
  1. Round : coccus (plural : cocci)
  2. Rod : Bacillus (bacilli)
  3. Curved rod : Vibrio (vibros)
  4. ## Spiral : Spirillum (spirilla)
  5. Pleomorphic : bacteria that can have multiple forms or shapes (FST1101B)
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8
Q

Name the different arrangements of bacteria cells (e.g. singular / plural / in fours / in chain / in cluster)

A
  1. Single : Coccus / cocci
  2. Pair : Diplococcus (diplococci)
  3. Four cells in a SQUARE : tetrad (tetrads)
  4. in a CHAIN : streptococcus (“strep” –> “strap’”)
  5. Cluster : Staphylococcus (staphylococci)
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9
Q

What is the function of a flagella in a bacterial cell?

A

To provide mobility to the bacteria

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10
Q

What are the names for the different number of flagella on a bacterial cell?

A
  1. Monotrichous – a single flagellum
  2. Amphitrichous – a single flagellum at both ends
  3. Lophotrichous – numerous flagella as a tuft at one end of the cell
  4. Peritrichous – numerous flagella all over the cell
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11
Q

What is the name of the substance found in the cell walls of both gram positive and negative bacteria? What is it made of?

A

Peptidoglycan

Peptidoglycan is a polymer made of sugars and amino acids that forms a mesh-like layer outside plasma membrane of bacteria.

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12
Q

What is the difference between the cell wall of gram positive and gram negative bacteria?

A

Gram positive bacteria has a thick layer of peptidoglycan on top of the plasma membrane

Gram negative bacteria only has a thin layer of petidoglycan in between the inner and outer membrane of the plasma membrane

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13
Q

to identify if a bacterial cell is gram positive or negative, the gram staining test can be used. What colour will the solution be in both gram positive / negative bacteria?

A

Gram positive bacteria : gram stain turns purple (blue)

Gram negative bacteria : gram stain turns pink (red)

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14
Q

Which of the processes require energy?

  1. Simple diffision
  2. Passive transport
  3. Active transport
A
  1. Active transport
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15
Q

How is bacteria named?
What are the conventions when naming (italicise, captialisation etc)

A

Using the bionomial nomenclature :

Genus species
– both are italicised
– capitalise the first letter of genus
– don’t need to capitalise first letter of species

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16
Q

What is a serotype/serovar?

A

seroTYPE, seroVAR(iation)

It is a distinct variation within a species of bacteria

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17
Q

How are bacteria classified into their various serovars?

A

They are classified together based on their cell surface antigens

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18
Q

Serovar in the naming convention of bacteria is italicised. True or False?

A

False, not italicised

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19
Q

Note : E coli naming convention

E coli O157 : H7

What do the letters and numbers of the naming suggest?

A

O157
- O refers to the somatic antigen (antigen on the cell surface)
- 157 refers to the 157th variation (out of the 173 types of somatic antigens)

H7
- H refers to the flagella antigen
- 7 refers to the 7th type (out of 56 ) types of flagella antigen

**There is antigen for capsular antigen, denoted with letter K and there are 103 types of antigens

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20
Q

Why can’t bacteria cells grow infinitely and reach a limit?

A

As the bacterial cell grows, the (surface) area-to-volume ratio decreases, leading to less efficient transport of nutrients

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21
Q

Do young cells or old cells have a larger surface area-to-volume ratio?

A

Young cells

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22
Q

When bacteria cells grow too big, what process do they undergo?

A

Binary fission

  • Understand the mechanism behind it
23
Q

What is generation time (G) of a bacteria?

A

It is the time that a single cell takes to divide into two.

24
Q

write down the equation involving initial number of cells (x), final number of cells (z), generation time (G) and duration of the study (t)

A

x. 2^(t/g) = z

25
Q

What does the growth curve show?

A

It shows the evolution of viable bacteria as a function of time

Viable : bacteria that are metabolically or physiologically active – meaning can reproduce / grow

26
Q

There are different ways of measuring the amount of bacteria cells which results in different growth curves. Two of them are :

  1. Optical Density (OD)
  2. Colony forming units (CFU)

What does OD / CFU mean?

A
  1. OD – Optical density measures the degree of light scattering caused by the bacteria within a culture.
    It counts both live and dead cells in a bacterial population
  2. CFU – colony-forming unit is a unit which estimates the number of microbial cells in a sample that are viable, able to multiply via binary fission under the controlled conditions
27
Q

What are the 3 unique features of bacteria?

A
  1. Ability to produce endospores
  2. Biofilm formation
  3. Quorum sensing
28
Q

What are the 2 of the few main kinds of bacteria GENERA which can produce endospores?

A
  1. Gram positive bacillus
  2. Clostridium
29
Q

What are endospores?

A

Endospores are dormant (inactive) alternate life forms

(produced by the genus Bacillus, the genus Clostridium, and a number other genera of bacteria, including Desulfotomaculum, Sporosarcina, Sporolactobacillus, Oscillospira, and Thermoactinomyces.)

30
Q

Where are endospores located in a bacteria cell?

A

Located in the center/off-center/terminal of the cell –> causes buldging of the cell

31
Q

Endospores are more resistant to physical and chemical antimicrobial treatments. True or false?

A

True

32
Q

What are the 2 metabolic forms of endospores (in terms of how active they are)?

Are they capable of transforming into other forms?

A

metabolically…

  1. inactive
  2. dormant (having normal physical functions suspended or slowed down for a period of time; in or as if in a deep sleep.)

but are capable of emerging as vegetative cells (normal cells which are actively growing, excluding the cells involved in production of gametes)

33
Q

What is a biofilm made up of?

A

A biofilm is made up of any group of microorganisms in which cells stick to each other and often to a surface.

34
Q

How do biofilms form? (FST1101B)

A

Free-floating microorganisms attach to moist surface using pili –> bacteria secrete various biomolecules –> a layer of slime forms around exposed surfaces of microorganisms

35
Q

In a biofilm, MO cells become embedded within a slimy extracellular polymeric substances (EPS). What biomolecules is EPS a conglomeration (assortment) of ?

A
  1. Polysaccharides (long chain sugars)
  2. Proteins
  3. DNA
36
Q

What is quorum sensing?

A

It is a way in which bacteria communicate with each other using chemical signal molecules

37
Q

How do bacteria communicate with each other through chemical means?

A

Bacteria cells …

  1. produce
    2, release
  2. detect and
  3. respond

to small hormone-like molecules known as autoinducers (AIs)

38
Q

What does quorum sensing allow bacteria to do? [2]

A

It allows bacteria to …

  1. monitor the environment for OTHER bacteria
  2. alter behaviour on a population wide scale in response to changes in the number and/or species present in a community
39
Q

YEASTS

Are they unicellular or multicellular?

What is their relevance with foods?

A
  • Unicellular
  • Yeasts are involved in food fermentation / spoilage
40
Q

YEASTS

How do yeasts reproduce?

A
  • Mostly reproduce asexually through budding, or sexually, depending on species
41
Q

Yeasts are capable of forming _____ on _____ culture media.

A

Colonies, solid

42
Q

MO(U)LDS
Are they unicellular or multicellular?

What is their relevance with foods?

A
  • Multicellular
  • They are involved in food fermentation / spoilage / safety
43
Q

MOULDS
Under what kinds of conditions do moulds grow in?

A

Harsh conditions, best in warm and humid envrionments

  • low pH
  • with oxygen (strict aerobes)
44
Q

MOULDS
How can moulds be an issue to food safety?

A

Moulds can produce mycotoxins (such as secondary metabolites, Aflatoxin, Patulin, Orchratoxin etc).

Mycotoxins are poisonous substances which can cause food poisoning and make people physically sick

45
Q

MOULDS
How do moulds reproduce?

A

They form spore, which are produced asexually (most commonly) and sexually, depending on the species

46
Q

Viruses are non-living things because they cannot reproduce by themselves. True or False?

A

True, viruses need a host cell for multiplication

47
Q

What is the genetic material held inside the virus?

A

A single type of nucleic acid, DNA/RNA

  • which may be single stranded (ss) or double stranded (ds) [number of strands]
  • linear or circular [shape]
48
Q

Viruses do not have cell walls, but a _____ _____.

The _____ _____ is made of ?

A

virus capsid

  • made of repeating protein subunits
49
Q

What is the name of the structure that some viruses possess, and some don’t?

A

Lipid envelope

50
Q

What is the difference between viruses that have a lipid envelope and viruses that don’t? (in terms of resistance)

A

Viruses with a lipid envelope are less resistant, as the lipid envelope is much more senstive and fragile compared to the virus capsid

51
Q

Food borne viruses usually (possess/ dont possess) a lipid envelope

A

Dont possess

52
Q

What are the 3 general properties of viruses?

A
  1. they infect all known organisms
  2. Cause a range of diseases
  3. Display diversity of morphology (shapes) and genetic makeup
53
Q
A

Y2S1_FST2110 - Microbiology and fermentation (12 decks)

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