This document discusses the various sources of foodborne microorganisms, including the atmosphere, soil, water, plants, and animals. It describes the typical microbial flora found in each environment and how microbes from these sources can contaminate foods and potentially cause spoilage or foodborne illness. The conclusion emphasizes that understanding the natural and transient microflora of foods is important for ensuring food safety during storage and preventing microbial growth.

1. Presented by
D. Mona Othman Albureikan
Food Microbiology
Sources of Foodborne
microorganisms

2. - Micro-organisms may be found everywhere
in a very wide range of habitats.
- Many micro-organisms is the atmosphere,
suspended in the air.
- The atmosphere forms an important way for
the spread of many micro-organisms, and later
the contamination of foods.
Sources of Foodborne
microorganisms

3. - Because human food sources are of plant and
animal origin, it is important to understand the
biological principles of the microbial biota
associated with plants and animals in their natural
habitats and respective roles.
Sources of Foodborne
microorganisms

4. - Micro-organisms as agents of
food spoilage or food poisoning,
it will be necessary to examine
the natural flora of the food
materials themselves, the flora
introduced by processing and
handling, and the possibility of
chance contamination from the
atmosphere, soil or water.
Sources of Foodborne microorganisms

5. -Bacteria can grow in the
atmosphere but they may be
exposed to the following
destructive agents :
1- Radiant energy of the sun.
2- Chemical activity of
gaseous oxygen.
Bacterial habitat:
AIRBORNE BACTERIA

6. AIRBORNE BACTERIA
- The bacterial flora can be
shown to be dominated by
Gram-positive rods and
cocci unless there has been
a very recent contamination
of the air by an aerosol
generated from an animal or
human source, or from
water.

7. - The pigmented colonies
will often be of
micrococci or
corynebacteria.
- The large white-to-
cream coloured colonies
will be of aerobic
sporeforming rods of the
genus Bacillus.
AIRBORNE BACTERIA

8. - The filamentous bacteria
belonging to Streptomyces
or a related genus of
actinomycetes.
AIRBORNE BACTERIA

9. AIRBORNE BACTERIA
-The air of farmyard barns may contain many millions of
spores of actinomycetes per cubic metre and some
species, such as Thermoactinomyces vulgaris and
Micropolyspora faeni , can cause the disease known as
farmer’s lung.
- Actinomycetes are rarely implicated in food Spoilage.
- Geosmin-producing strains of Streptomyces may be
responsible for earthy smell and strange flavours in
drinking water.

10. - The pigments may protect
microorganisms from damage by both
visible and ultraviolet radiation of
sunlight.
- Also, thick cell walls of Gram-positive
bacteria afford protection from drying.
- The endospores of Bacillus and the
conidiospores of Streptomyces are
resistant to damaging effects of
suspension in the air.
AIRBORNE BACTERIA

11. - The effects of radiation
and drying are enhanced
by another phenomenon,
the ‘open air factor’
which causes even more
rapid death rates of
sensitive Gram-negative
organisms such as
Escherichia coli.
AIRBORNE BACTERIA

12. - Bacteria have no active mechanisms for becoming
airborne. They are dispersed on dust particles
disturbed by physical agencies, in droplets of water
generated by any process which leads to the
formation of an aerosol.
AIRBORNE BACTERIA

13. Airborne Fungi
- Some of the most important moulds in food
microbiology do not have active spore dispersal
mechanisms but produce large numbers of small
non wettable spores which are resistant to dryng
and light damage.

14. - They become airborne in
the same way as fine dry
dust particles by physical
disturbance and wind.
- Spores of Penicillium and
Aspergillus seem to get
everywhere and they are
responsible for food
spoilage.
Airborne Fungi

15. - The sporophores of
fungi such as
Cladosporium react by
throwing their easily
detached spores into the
atmosphere .
- Species such as
Cladosporium herbarum
grow well at refrigeration
temperatures and form
black colonies on the
surface of food such as
chilled meat.
Airborne Fungi

16. -Yeasts, which are a part of the
normal microbial flora of the leaf
surfaces of plants, are usually present
in highest numbers in the atmosphere
when the humidity is at its highest.
- Many fungi have mechanisms for
firing their spores into the atmosphere
, which requires a high relative
humidity.
Airborne Fungi

17. MICRO-ORGANISMS OF SOIL
* The soil environment is extremely complex
and different soils have their own divers flora of
bacteria ,fungi ,protozoa and algae.
* The soil is a rich place of microorganism that
it has provided many of the strains used for the
industrial production of antibiotic, enzymes,
amino acids, vitamins and other products used in
both the pharmaceutical and food industries.

18. • Soil microorganisms participate in the recycling
of organic and nitrogenous compounds which is
essential of the soil to support the active growth
of plants.
• But this ability to degrade complex organic
materials makes these same micro-organisms
potent spoilage organisms if they are present on
foods.
MICRO-ORGANISMS OF SOIL

19. - Many soil bacteria
and fungi produce
resistant structures,
such as the
endospores of
Bacillus and
Clostridium, and
Chlamydospores.
MICRO-ORGANISMS OF SOIL

20. - Bacterial endospores
are especially resistant to
high temperatures, and
their common occurrence
in soil makes this a
strong source of spoilage
and food poisoning bacilli
and clostridia.
MICRO-ORGANISMS OF SOIL

21. MICRO-ORGANISMS OF WATER
- Fresh water and the sea
contain many species of
microorganisms adapted to
habitats.
- Marina bacteria are described
as oligotrophic psychrophiles
with a requirement for sodium
chloride for optimum growth.

22. - The surfaces of fish in cold water have a bacterial
flora which can break down macromolecules, such
as proteins, polysaccharides and lipids.
- Under such conditions,
once a flora has reached
between 107and 108, it
could be responsible for
the spoilage.
MICRO-ORGANISMS OF WATER

23. -During the handling of
fish, the natural flora of
the environment will be
contaminated with
organisms associated with
man, such as members of
the Enterobacteriaceae
and Staphylococcus, which
can grow well at 30–37 C°.
MICRO-ORGANISMS OF WATER

24. - The seas around the coasts are affected by
freshwater microorganisms and human activities.
-The sea has become a
appropriate dump for sewage
and other waste products.
-The sea can disperse such
materials and render them
harmless.
MICRO-ORGANISMS OF WATER

25. -Many shellfish used for food grow in these polluted
coastal waters and they feed by filtering out particles
from large volumes of sea water.
MICRO-ORGANISMS OF WATER
-If these waters have been
contaminated with sewage there is
always the risk that enteric organisms
from infected shellfish may be present
and will be concentrated by the filter
feeding activities of shellfish.

26. - Severe diseases
such as hepatitis or
typhoid fever have been
caused by eating
contaminated oysters
and mussels which seem
to be perfectly normal
in taste and appearance.
MICRO-ORGANISMS OF WATER

27. -In warmer seas even unpolluted
water may contain significant
numbers of Vibrio parahaemolyticus
and these may also be concentrated
by filter-feeding shellfish.
-This organism may be responsible
for outbreaks of food poisoning
especially associated with sea
foods.
MICRO-ORGANISMS OF WATER

28. -Fungi are also present in both marina and fresh water
but they do not have the same level of significance in
food microbiology as other microorganisms.
-There are groups of aquatic fungi including some
which are serious pathogens of molluscs and fish.
- It could be responsible for spoilage of a food that
associated with water such as a salad crop cultivated
with overhead irrigation from a river or lake.
MICRO-ORGANISMS OF WATER

29. -Photosynthetic, the cyanobacteria, or blue-green
algae (prokaryotes) and dinoflagellates (eukaryotes),
have an impact on food quality and safety.
-Both these groups of microorganisms can produce
very toxic metabolites which become concentrated in
shellfish without apparently causing them any harm.
-When consumed by humans, however, they can
cause a very nasty illness such as paralytic shellfish
poisoning.
MICRO-ORGANISMS OF WATER

30. MICRO-ORGANISMS OF PLANTS
-All plant surfaces have a natural flora of
microorganisms which may be referred to as;
A- The phylloplane flora, for that of the leaf surface.
B- The rhizoplane flora for the surface of the roots.

31. -The bacterial flora of aerial
plant surfaces includes;
A- Gram-negative rods, such
as Pectobacterium, Erwinia,
Pseudomonas and
Xanthomonas.
B- A numerically smaller flora
of fermentative Gram positive
bacteria such as Lactobacillus.
MICRO-ORGANISMS OF PLANTS

32. - The moulds, yeasts and
bacteria not harm young
plant surfaces so, they
are not cause any
problem in the spoilage of
plant products after
harvest.
-There are yeasts of the genera Sporobolomyces
and Bullera on plant leaf surfaces.
MICRO-ORGANISMS OF PLANTS

33. - But, when humans break into this cycle and harvest
plant products such as fruits and vegetables, these
same organisms may cause spoilage problems during
prolonged periods of storage and transport.
- In the natural cycling of organic matter these
organisms would help to break down the complex
plant materials to carbon, nitrogen and other
elements as nutrients for the next round of plant
growth.
MICRO-ORGANISMS OF PLANTS

34. - Erwinia carotovora is a pathogen of the potato
plant causing blackleg disease.
MICRO-ORGANISMS OF PLANTS

35. -The senescent plant
carrying the cereal
Cladosporium, Alternaria.
- After harvest and reduction
of the grain, the field flora
decrease in numbers and
replaced by a storage flora
which includes species of the
Penicillium and Aspergillus.
MICRO-ORGANISMS OF PLANTS

36. -Some genera of fungi, such as Fusarium, contain a
spectrum of species;
A- Some of which are specialized plant pathogens.
B- Others saprophytic field fungi.
C- Others can grow during the initial stages of storage.
MICRO-ORGANISMS OF PLANTS

37. - Aspergillus flavus, a very
important species because of its
ability to produce the carcinogenic
metabolite known as aflatoxin, is
not just a storage mould as was
once believed, but may infect the
growing plant in the field and
produce its toxic metabolites
before harvesting and storage
MICRO-ORGANISMS OF PLANTS

38. MICRO-ORGANISMS OF ANIMAL
ORIGIN
- All healthy animals carry a complex microbial
flora.
- The surfaces of humans and other animals are
exposed to air, soil and water.
- There will always be the possibility of
contamination of foods and food handling equipment
and surfaces with these environmental microbes by
direct contact with the animal surface.

39. - The surface of the skin is not
a favourable place for most
microorganisms since it is;
1- Usually dry.
2- Has a low pH ( the organic
acids secreted from some of
the skin pores).
The skin
MICRO-ORGANISMS OF ANIMAL
ORIGIN

40. - The microorganisms are characteristic for each
species of animal and, in humans, the normal skin
flora is dominated by Gram-positive bacteria from
the genera Staphylococcus, Corynebacterium and
Propionibacterium.
The skin
MICRO-ORGANISMS OF ANIMAL
ORIGIN

41. -Staphylococcus aureus is
carried on the mucous
membranes of the nose.
- Some strains of this pecies
can produce a powerful
toxin capable of eliciting a
vomiting response.
MICRO-ORGANISMS OF ANIMAL
ORIGIN
The Nose and Throat

42. CONCLUSIONS
- We have described some of the major sources of
microorganisms which may contaminate food and cause
problems of spoilage or create health risks when the
food is consumed.
- Most foods have a natural flora and acquire a
transient flora derived from their environment.
- To ensure that food is safe and can be stored in a
satisfactory state, it is necessary to either destroy the
microorganisms present, or manipulate the food so that
growth is prevented.