1 - Food is An Ecosystem Flashcards
Phototrophs eat ____________ and make ____________
eat sunlight / CO2, make O2
Anaerobic Methanogens eat ____________
CO2
Anaerobic Methanogens make
CH4
Aerobic Methanotrophs eat ____________
CH4
Aerobic Methanotrophs make ______________
CO2
Ecosystem is ___________________
a series of interactions between the environment and the organisms that inhabit it
Food ecosystems, like all ecosystems, are impacted by the generation and utilization of ___________
energy
TRUE OR FALSE: The human (and animal) gastrointestinal tracks are also ecosystems
TRUE
Food ecosystems (especially when they include human pathogens) affect _______________, and may result in illness
host-ecosystems
Food ecosystems are composed of _______ and ________ factors
intrinsic and extrinsic
Intrinsic factors are factors inherent to the food including:
pH, water activity, nutrients
Extrinsic factors are factors external to the food
Temperature, gaseous atmosphere
TRUE OR FALSE: Intrinsic and extrinsic factors may change over time as bacteria grow and produce bi-products
TRUE
Food can be heterogenous on a micrometer scale and may contain several ________ (aerobic vs anaerobic)
microenvironments
Describe in detail the bacterial growth curve :
y-axis: number of bacterial cells
x-axis: time
lag phase, log or exponential growth phase, stationary phase and death phase
Bacteria must have ________ for building the array of chemical substances of which they are composed (anabolism)
carbon
Autotrophic (cyanobacteria) bacteria obtain their carbon source from
CO2 through carbon fixation
Heterotrophic (Listeria monocytogenes) bacteria obtain their carbon source from
organic compounds
Mixotrophic bacteria obtain their carbon source from
combining auto and heterotrophy
Bacteria must have a source of ________ for living (catabolism)
energy
Chemotrophic bacteria obtain their energy from:
external chemical compounds
Phototrophic bacteria obtain their energy from:
light
Bacteria must have a source of ______ to be used in energy conservation and biosynthetic reactions
electrons
Lithotrophic bacteria obtain their reducing equivalents from:
inorganic compounds
Organotrophic bacteria obtain their reducing equivalents from
organic compounds
Bacteria must have an electron _________
acceptor
Aerobic organisms use _______ as a terminal electron acceptor (this is the most energetically favourable reaction)
oxygen
Fermentation uses _________ as a terminal electron acceptor, therefore, fermentative organisms are considered _________
organic carbon, anaerobes
If an organism can grow with or without oxygen they are called __________
facultative anaerobes
succinate fermentation or oxalate fermentation are examples of ______
very low energy yielding fermentation reactions
Catabolism = energy ________
generation
Anabolism = energy ________
consumption
Lactic acid bacteria produce relatively large quantities of ___________
lactic acid from carbohydrates (ex: lactobacillus in yogurt)
Proteolytic bacteria hydrolyze _______ because they produce _________________ (Clostridium botulinum)
proteins, extracellular proteinases
Lipolytic bacteria hydrolyze ________. because they produce _____________
triglycerides, extracellular lipases
Thermophilic bacteria:
bacteria that are able to grow at 50C and above
Thermoduric bacteria
able to survive pasteurization temperatures
Psychrotrophic bacteria
able to grow at refrigerated temperatures (below or equal to 5C)
Cryophilic bacteria
able to grow at freezer temperatures (below or equal to 0C)
Halophilic bacteria
able to survive high salt concentrations (equal or above to 10%)
Aciduric bacteria
able to survive low pH
Osmophilic bacteria
able to grow at a higher osmotic environment
Spore formers:
able to produce spores (C.botulinum)
Coliforms:
used as an index for sanitation
Fecal coliforms:
used as an index for sanitation, presence indicates fecal contamination
Enteric pathogens:
can cause gastrointestinal infection
Relative abundance of a specific type of microorganism will depend on _______ and ________
intrinsic and extrinsic factors
Why is milk a good environment for microbial growth?
- high carbohydrates (lactose)
- high protein
- both great sources of carbon and energy for microbial growth
Several microbes in fish are _______
halophiles
Fish harvested from water polluted with human waste can contain several varied pathogens like _________
Vibrio cholerae
Microorganisms can grow rapidly in fish because of ___________________________
high water availability, the pH of the tissue, and the availability of carbon and nitrogen
What are the sources of contamination for fruits and vegetables:
soil, water, air, animals, insects, birds, equipment, harvesters,etc
In canned foods, if pH is lower than 4.6 pathogenic mesophiles ___________
cannot germinate and produce illness causing toxins (C.botulinum)
If pH is above 4.6 pathogenic mesophiles are not an issue, but if cans are temperature abused (stored over 40C) :
thermophilic spores can germinate and cause spoilage
T or F: Staphylococcus cannot grow in canned foods, however, it’s toxins can survive the canning process
T
