General Dairy Bacteriology Flashcards
What are bacteria?
Single-celled organisms that can only be seen with a microscope
All processes needed for life occur within the cell.
What is the magnification required to see bacteria?
1,000X
A microscope is necessary to observe bacteria.
In what unit are bacteria measured?
Microns
1 micron = 1/1,000 mm = 1/25,000 inch.
What are the three categories of bacteria?
- Beneficial
- Pathogenic
- Spoilage
Each category has distinct roles and impacts, especially in the dairy industry.
What are beneficial bacteria responsible for?
Food fermentations (e.g. cheese)
These bacteria play a crucial role in dairy processing.
What do pathogenic bacteria cause?
Disease
These bacteria pose health risks in food products.
What do spoilage bacteria cause?
Food products to break down
This is a primary concern in the dairy industry.
What shape are cocci bacteria?
Spherical
Cocci can occur as single cells, pairs, chains, or clusters.
What is the size range for cocci bacteria?
0.4-1.5 microns
This size range is typical for cocci found in milk.
What shape are bacilli bacteria?
Rod shaped
Bacilli can occur as single cells, pairs, or chains.
What is the size range for bacilli bacteria?
0.5-30 microns
This range indicates the variability in bacilli size.
How are individual bacteria named?
By Genus and species (e.g. Bacillus cereus)
This naming convention applies to all living organisms.
What are the unusual shapes of bacteria that are less common in milk?
Spiral, helical, or club shaped
These shapes are generally not very prevalent in dairy products.
What is a common method to visualize bacteria in milk?
Staining a dried milk smear with a specific ‘milk-stain’
An example of a milk-stain is the Levowitz-Weber stain.
What is the primary classification of most bacteria?
Gram-positive or Gram-negative
What is the purpose of the Gram stain procedure?
To view and differentiate bacteria under a microscope
What are endospores?
Protective, dormant structures that allow an organism to survive under adverse conditions
What triggers the formation of bacterial spores?
Unfavorable conditions such as lack of nutrients
What color do Gram-positive bacteria stain?
Blue
What color do Gram-negative bacteria stain?
Red
What are some examples of Gram-positive bacteria?
- Bacillus
- Streptococcus
- Staphylococcus
What are some examples of Gram-negative bacteria?
- Pseudomonas
- E. coli & other coliform bacteria
What does Gram-variable mean?
Stains blue or red depending on conditions; most are Gram-positives
What are some conditions that bacterial spores resist?
- Heat
- Drying
- Nutrient deprivation
- Presence of chemicals or sanitizers
Which type of bacteria do not survive pasteurization?
Gram-negative bacteria
What type of spores are produced by only a few select groups of bacteria?
Endospores
What type of bacteria are commonly spore-forming and important to dairy?
Gram-positive rods
Where are spores commonly found?
- Soil
- Manure
- Other environmental sources
Fill in the blank: Spores can remain dormant for ______ periods of time.
extended
True or False: Spores are produced by many different groups of bacteria.
False
What happens when conditions become favorable for spores?
A spore can germinate and return to an actively growing state
What is the significance of spore-forming bacteria in dairy spoilage?
Gram-negative bacteria spoil milk faster under refrigeration compared to Gram-positive spoilage organisms
