what are the characteristics of microbes?
• 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
What is cross contamination?
Cross contamination describes the transfer of microbes to a clean surface.
Env. costs of microbes to ag?
nutrient leaching crop/animal disease recalcitrant pollutants pathogen emergence methanogenesis env’l bioburden
Env. pros of microbes to ag?
nutrient cycling biological control bioremediation antibiotics, bacteriophages rumen microbes natural fertilisers rhizosphere
-enhanced sustainable
productivity
How are microbes used for disease control?
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)
What’s a bioburden?
A bioburden is when you have more biomass than can readily decompose.
What is bioremediation?
– 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”
What is the effect of composting?
Composting sterilizes manure: reaches pasteurizing temperature and retaining nutrients.
- Like warm, damp, anaroebic conditions. Like tips.
How are bacteria responsible for methanogenesis?
Bacteria in rumen break down cellulose, generating methane. Can be burnt as biogas.
What’s the rhizosphere>
The rhizosphere is a community of organisms around the plant roots. It likes methane. Protects plant roots and enhances growth.
What are the three key aspects of food microbiology?
- Food production
- Spoilage
- Food safety (pathogens)
on farm practices affecting microbial food quality and safety?
• intensification of agriculture and emergence of “new” pathogens • quality of irrigation water • plant diseases • “organic” production • post-harvest handling • farm hygiene/animal husbandry
How does pathogen emergence occur?
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)
Why is quality of irrigation water important?
• 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)
importantce pf plant disease
• 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
Issues of microbial stuff on organic food prod.
• 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
Burden of spoilage?
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
how can post-harvest handling impact food safety?
• 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
How on farm hygiene affects food safety?
• 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)
Microbes summary
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
