Microbiology

Question 1

what are the characteristics of microbes?

Answer 1

• ubiquitous and mobile
• enormous metabolic diversity
• can generate energy from inorganic compounds
• programmed to procreate
• multiply rapidly when conditions allow, some can
persist indefinitely when conditions don’t allow
growth

Question 2

What is cross contamination?

Answer 2

Cross contamination describes the transfer of microbes to a clean surface.

Question 3

Env. costs of microbes to ag?

Answer 3

nutrient leaching
crop/animal disease
recalcitrant pollutants
pathogen emergence
methanogenesis
env’l bioburden

Question 4

Env. pros of microbes to ag?

Answer 4

nutrient cycling
biological control
bioremediation
antibiotics, bacteriophages
rumen microbes
natural fertilisers
rhizosphere

-enhanced sustainable
productivity

Question 5

How are microbes used for disease control?

Answer 5

intensive agriculture
– antibiotic use and emergence of resistance
– epidemic disease, emergence of new pathogens (gene transfer)

• biological control
– antibiotics
– calicivirus (control of rabbits)
– entomopathogenic fungi, nematodes, Bacillus
thuringiensis (Bt), (control of insects)
– bacteriophages (control of bacterial pests, e.g.,
Xanthomonas on walnuts, foodborne pathogens)

Question 6

What’s a bioburden?

Answer 6

A bioburden is when you have more biomass than can readily decompose.

Question 7

What is bioremediation?

Answer 7

– manipulation of microbes to decompose pollutants
(inc. agricultural chemicals and organic wastes)
=> May need several types of microbe to break down different compounds to be effective.

– encourage microbial growth (water, warmth,
nutrients); microbial “consortia”

Question 8

What is the effect of composting?

Answer 8

Composting sterilizes manure: reaches pasteurizing temperature and retaining nutrients.
- Like warm, damp, anaroebic conditions. Like tips.

Question 9

How are bacteria responsible for methanogenesis?

Answer 9

Bacteria in rumen break down cellulose, generating methane. Can be burnt as biogas.

Question 10

What’s the rhizosphere>

Answer 10

The rhizosphere is a community of organisms around the plant roots. It likes methane. Protects plant roots and enhances growth.

Question 11

What are the three key aspects of food microbiology?

Answer 11

• Food production
• Spoilage
• Food safety (pathogens)

Question 12

on farm practices affecting microbial food quality and safety?

Answer 12

• intensification of agriculture and emergence of
“new” pathogens
• quality of irrigation water
• plant diseases
• “organic” production
• post-harvest handling
• farm hygiene/animal husbandry

Question 13

How does pathogen emergence occur?

Answer 13

Pathogen emergence occurs through gene transfer.

• Associated with feedlots and caged chooks, and antibiotics
  e. g., ‘mad cow’ disease (‘prion’) – resulted from feeding animal protein back to animals (+ change to the rendering process)

Question 14

Why is quality of irrigation water important?

Answer 14

• some crops are eaten with little further processing
• some pathogens are difficult to eliminate by simple
washing processes
• pathogens in irrigation water or processing water
can remain on the product (or be drawn into the
product) – and can lead to foodborne illness

• increased pressure on water re-use
– e.g., Cole River valley irrigation scheme uses effluent from Rosny STP (but not on food crops)

Question 15

importantce pf plant disease

Answer 15

• can cause food spoilage in the field, prior to harvest
(“field fungi”)
• some diseases of living plants translate into spoilage
problems upon storage of fruits/vegetables/nuts etc
(“storage fungi”)
• some plant pathogens create opportunities for
spoilage organisms to enter the edible portion

Question 16

Issues of microbial stuff on organic food prod.

Answer 16

• composts can contain pathogenic microbes
– composting has to be managed and controlled
• manure certainly contains pathogenic microbes
– manure handling must be appropriate to application (e.g.,
not near food crops)
• less pesticides, less protection against some
pathogens or spoilers

Question 17

Burden of spoilage?

Answer 17

economic losses:
– 10 - 20% of cereals and legumes lost through
spoilage
– 20% of all fruits and vegetables lost through
spoilage
– 25% of highly perishable foods spoiled before
consumption

Question 18

how can post-harvest handling impact food safety?

Answer 18

• cooling
– for preservation & safety e.g., milk, fruit and vegetables

• storage conditions
– temperature, moisture – must be controlled to prevent bacterial or fungal growth

• physical damage can potentiate spoilage
• stressed animals can shed pathogenic bacteria prior
to slaughter

Question 19

How on farm hygiene affects food safety?

Answer 19

• control of infections in food animals
• mastitis in dairy cows (food-borne pathogens)
• cleanliness when milking
– cows themselves
– milking equipment (biofilms?, soil microbes)
• withholding periods for crops sprayed with
pesticides
• (irrigation and wash water)

Question 20

Microbes summary

Answer 20

microbes not visible in ecosystems but have a massive
influence on productivity and sustainability
• benefit, but also cause problems in, agriculture and
food quality/safety
• microbes are incredibly diverse, versatile, mobile,
and ‘find their way’ into favourable ecosystems
– means that there is buffering to environmental change but…
– managing environmental microbiology can be like herding cats