LECTURE 19 - Microbes, Food and Nutrition

Question 1

good roles of microbes in the food production chain

Answer 1

1. production :
rumen microbes help cows digest grass
symbiotic fungi enhance plant growth
Soil microbes recycle wastes into nutrients

2. processing
Many foods require fermentation

3. restaurants/retail
Some microbes are food sources (fungi, algae)

4. consumption
gut microflora beneficial to health

Question 2

bad roles of microbes in the food production chain

Answer 2

1. production :
Pathogens infect animals and plants
Irrigation water can be contaminated with pathogens
Post-harvest contamination can ruin crops

2. processing
Factories can be contaminated by microbes

3. distribution
Refrigeration needed to stop microbial growth

4. restaurants/retail
Poor hygiene–> food poisoning
5. consumption
Poor gut microbiota –> causes poor health

Question 3

steps in the food production chain

Answer 3

1. production
2. processing
3. distribution
4. retail
5. home preparation
6. home consumption
7. restaurant
8. restaurant preparation
9. restaurant consumption

Question 4

Enhancing food production -microbes in soil

Answer 4

Enhancing food production
Microbes maintain soil health by:
– Fixing nitrogen (N2–> NH 4+)
– Breaking down organic wastes into inorganic nutrients
– Suppressing animal + plant pathogens
– Breaking down toxins e.g. pesticides

Question 5

Enhancing food production -microbes in animals

Answer 5

Enhancing food production - microbes in animals
* Cellulose: a sugar polymer, abundant in
plants, carbon-rich, but difficult to digest
* Rumen microbes break down cellulose
–> sugars –> organic acids, CO2 , CH 4
* Organic acids and microbial cells are then
digested by animal as nutrients
Microbes enable animals to digest cellulose :

• CH 4 from ruminants –> climate change :(

Question 6

Enhancing food production - microbes in plants

Answer 6

Microbes promote plant growth via mutualism:
* Mutualism: ecological interaction
where both partners benefit
* Mycorrhizal fungi (in most plants)
enhance water + inorganic nutrient
uptake, receive sugars from plant
* Rhizobium bacteria (in legume roots)
fix nitrogen, receive sugars in return

Question 7

Plant pathogens

Answer 7

• Just like humans and animals, plants are subject to diseases caused by microbial pathogens
• Fungi and viruses are the main problems
• Crop pathogens cause global losses of
  ~30% of total yield (approx. $1 trillion!)

Tobacco mosaic virus is simple (only 3 genes)–> … but it can infect many crops !
tobacco –> tomatoes –> cannabis

Question 8

Plant pathogens … emerging diseases

Answer 8

• Sigatoka fungi threaten the survival of bananas globally –> Modern Cavendish bananas are all grown from cuttings, not seed
  –> genetically identical –> ALL equally susceptible
• Need to apply fungicides 50x per year, and fungus is rapidly evolving
  resistance … sound familiar?

Question 9

Animal pathogens

Answer 9

• Pathogens infecting animals inflict suffering, death, and
  massive economic losses (~20% of total production)
• Pathogens can be viruses, bacteria, fungi, or protists
• Modern agricultural practices can
  aggravate the microbial problems [for example, can create conditions conducive to the spread of diseases among animals. The close proximity of animals in large-scale farming operations can facilitate the rapid transmission of pathogens.]

e.g. Foot and mouth’ virus:
a devastating viral disease
infecting many farm animals

Question 10

foot and mouth virus

Answer 10

Foot and mouth disease (FMD) is a highly contagious viral infection, have serious consequences for livestock.

mainly spread from one animal to another through contact with bodily fluids, such as saliva, mucus, and discharge from the blisters and sores it causes.

develop symptoms like fever, blisters or sores on their mouths, tongues, and hooves (foot and mouth), and they might become lame or have difficulty walking. This can be very painful for the animals, and it can make them less productive.

Question 11

outbreak of foot and mouth disease

Answer 11

cause huge problems for farmers and the economy.

In the UK in 2001, 10 million animals were infected and had to be disposed–> lost £8 billion.

The outbreak in the UK happened because some pigs were given food that had waste products, including meat, from animals that were infected with the FMD virus.

Why is it significant?
* money
* not good for the animals that get sick
* hard to decide what to do with them
* have bad effects on the environment.
* raises ethical questions about how we treat animals and where we get their food.

Question 12

Zoonosis def

Answer 12

human infection arising from animals

Question 13

zoonosis

Answer 13

• Animal is a ‘vector’ for disease e.g. animal ticks can
  carry Borrelia bacteria (Lyme disease)

1. Microbes may be pathogenic to both animals and humans: Some microbes, like the rabies virus, can make both animals and humans sick.
   For example, if a dog gets rabies and bites a person, the person can also get sick with rabies.
2. Microbes that are normal flora for animals but can make humans sick: For instance, Salmonella bacteria can live in chickens without making them sick, but if people eat eggs or poultry contaminated with Salmonella, they can get sick.
3. Animals are vectors and carry disease: Some animals can carry disease-causing microbes and pass them on to humans. For example, ticks, tiny insects that attach to animals, can carry a bacterium called Borrelia that causes Lyme disease. When a tick bites a person, it can transfer the bacterium, and the person may get sick with Lyme disease.

Question 14

zoonosis example

Answer 14

covid —> caused by a virus called SARS-CoV-2
Original Host - Bat: it is thought that the virus initially existed in bats in a different form before it jumped to humans.

Intermediate Host - Pangolin: The pangolin, an endangered mammal, is suspected to have served as an intermediate host. This means that the virus may have first passed from bats to pangolins and then from pangolins to humans.

This zoonotic transmission likely occurred through the consumption or handling of pangolins which transferred to humans

Question 15

Enhancing food processing - Fermentation

Answer 15

• “Fermentation” has multiple meanings:
  – involves the use of microorganisms like fungi or bacteria to transform food
  – anaerobic metabolism of sugars –> alcohols, acids, CO 2.
  [microorganisms break down sugars and turn them into other substances, such as alcohols, acids, and carbon dioxide (CO2).]
• Examples:
  – Beer
  – Wine
  – Bread
  – Kimchi
  – Yogurt
  – Cheese
  – Pickles

Question 16

Fermented foods – beer production

Answer 16

barley + hops + water + yeast = beer
* Barley: source of sugars to support fermentation
* Hops: natural preservative, provide bitterness
* Yeast: ferments sugars to alcohol and CO2

Question 17

The hero of beer production:

Answer 17

Saccharomyces (brewer’s yeast)
–> a type of yeast that reproduces through a process called budding.

The mother cell / parent cell : the mature cell that has been actively growing and dividing –> daughter cell formed from the budding process –> detaches and independent

Saccharomyces also makes
wine, cider and other alcoholic
beverages. And it makes
bread rise. It’s a wonder-bug!

Question 18

Microbial food spoilage

Answer 18

Microbial food spoilage occurs when microorganisms, such as bacteria and fungi, contaminate and grow on food products.due –> produce enzymes it makes/secretes to break down the food, leading to changes in its texture, taste, and safety

• Big economic problem: Approx. 20% of all food is lost to
  microbial spoilage… approx. $1 trillion

Question 19

how to prevent microbial food spoilage

Answer 19

Spoilage prevention?

• Refrigeration
  [Low temperatures slow down the growth of most microorganisms and the enzymatic reactions that lead to spoilage. ]
• Preservatives
  [substances added to food to inhibit the growth of spoilage microorganisms and extend the shelf life of products. Common preservatives include salt, sugar, vinegar, and chemical additives like sodium benzoate or sulfur dioxide. These inhibit the growth of bacteria and fungi.]
• Fermentation
  [During fermentation, the beneficial microbes produce acids, alcohol, or other compounds that create an environment unfavorable for spoilage organisms; less susceptible to spoilage by harmful microorganisms]

Question 20

Food spoilage vs food poisoning

Answer 20

Food spoilage and food poisoning are distinct but related concepts when it comes to food safety:

1. Food Spoilage:
   
   • Definition: the deterioration of food quality due to various factors, such as microbial growth, chemical reactions, or physical changes.
   • Cause: growth and activity of spoilage microorganisms
2. Food Poisoning (Foodborne Illness):
   
   • Definition: Food poisoning, or foodborne illness, is the result of consuming food contaminated with harmful microorganisms (pathogens) or their toxins.
   • Cause: pathogenic microorganisms, such as certain strains of bacteria (e.g., Salmonella, E. coli), viruses (e.g., norovirus), or parasites (e.g., Giardia). These microorganisms produce toxins or directly infect the consumer.
   • Symptoms: nausea, vomiting, diarrhea, abdominal pain, fever, and other gastrointestinal or systemic symptoms. T

Question 21

Food ‘poisoning’ = Infection or Intoxication

Answer 21

food-borne infection and food-borne intoxication.

Food-Borne Infection:
microbes (microscopic organisms like bacteria or viruses) entering the body through contaminated food.
–> survive and grow in your gastrointestinal (GI) tract, specifically in your stomach and intestines.
–>they multiply, cause an infection in your gut.

e.g. Salmonella enterica.

Food-Borne Intoxication:
when you consume food that contains toxins produced by microbes. In this case, the microbes themselves may not necessarily grow inside your body.
–? toxins are harmful substances created by certain microorganisms when they are present in the food.
toxins = rapid impact on your body, leading to symptoms such as nausea, vomiting, and neurological issues, depending on the specific toxin.
e.g. Clostridium botulinum: produces a potent toxin that can be found in improperly canned or preserved foods. When ingested, this toxin can lead to serious and even life-threatening symptoms

Question 22

Food ‘poisoning’ risk factors

Answer 22

• Origins of food
  – determines types and
  numbers of microbes
  [raw chicken may have harmful bacteria like Salmonella, while fresh fruits and vegetables can carry bacteria from the soil.]
• Storage and Preparation
  – refrigeration : slow down the growth of harmful microbes.
  – raw/cooked : Cooking food thoroughly is also vital. Heat kills most harmful microbes. For instance, make sure meat is cooked to a safe internal temperature to kill any harmful bacteria.
• Human factors
  – hygiene !
  –> poor hygiene can introduce harmful microbes into food.
  –> wash your hands with soap before handling food.
  –> avoid cross-contamination by using separate cutting boards and utensils for raw and cooked foods.
  –> be cautious with food left out for extended periods; bacteria can multiply rapidly at room temperature.

Question 23

One Health concept in food production

Answer 23

• Maintaining a safe food supply depends on managing
  microbes at every stage in the production chain:
• SOIL
• PLANTS
• ANIMALS
• PEOPLE
• FACTORY
• KITCHEN

production/processing/distribution/retail

Question 24

The human gut microbiome

Answer 24

• Gut microbes are the most important element of our normal flora – these are primarily BACTERIA
• Approx 40 trillion bacteria in gut
  microbiome; now considered a
  separate body ‘organ’
  Microbiome analysis is
  now big business

Question 25

Gut microbiome depends on diet

Answer 25

High fibre diet
↑ Bacteriodetes

High protein & fat diet
↑ Firmicutes

Question 26

gut microbiome positively influence us?

Answer 26

– Proper food digestion [gut microbiome aids in the breakdown of complex carbohydrates and fibers in our diet]

– Resistance to pathogens [Beneficial bacteria in the gut can outcompete and suppress the growth of harmful microbes]

– Immune functioning [microbiome interacts with immune cells and helps train them to distinguish between harmful invaders and harmless substances]

– Mental health [balanced gut microbiome may influence mood, stress levels, and even conditions like anxiety and depression.]l

Question 27

gut microbe negative influence on us

Answer 27

• “Bad” microbiome linked to:
  – Allergies
  – Type 2 diabetes
  – Cancer
  – Obesity

Impact of antibiotics / probiotics / prebiotics
on the human microbiome is controversial

Question 28

Impact of Antibiotics / Probiotics / Prebiotics on gut microbiome

Answer 28

Impact of Antibiotics / Probiotics / Prebiotics:

Antibiotics: While antibiotics can be life-saving by targeting harmful bacteria, they can also disrupt the balance of the gut microbiome by affecting beneficial bacteria.

Probiotics: live beneficial microorganisms (often specific strains of bacteria) –> to potentially restore balance to the gut microbiome.
However, the effectiveness of probiotics and impact on individual can vary

Prebiotics: non-digestible fibers that serve as food for beneficial gut bacteria –> support the growth and activity of these bacteria.