INTRODUCTION AND HISTORY OF FOOD MICROBIOLOGY Flashcards
Microbial impact on foods
Positive effects such as
1.Food Fermentaion-flavors 2.Probiotic bacteria 3.Bacteriocins
Microbial impact on foods
Negative effects such as
- Spoilage
2. Lose of shelf-life 3.Foodborne pathogens
Cell division occurs on a
on a single plane (bacilli), muliple planes (cocci)
Listeria monocytogenes, Escherichia coli O157:H7, Salmonella, Shigella, Clostridium, Yersinia, Bacillus cereus,
Bacilli
Staphylococcus aureus
Cocci
Vibrio
Vibrio vulniicus,
Vibrio parahemolyicus
Campylobacter
Spirillum
What kinds of Bacterial Shapes ?
- Bacilli
- Cocci
- Vibrio
- Spirillum
what Structures External to the Cell Wall of Bacteria?
Flagella (H anigen)
Pili
Axial Filaments
Thin appendage; primary funcion moility
Flagella (H anigen)
Flagella Bacteria can be:
monotrichous means single
peritrichous means many around cell
✅❌
cocci are rarely moile
✅
✅❌
Generally only bacilli and vibrio posses flagella
✅
what is the Pili ?
- Short, thin hollow hair like structures, -primarily on Gram negaive
- Consist of a protein
✅❌
Pili have funcion regarding moility
❌ No .
common pili believed to have a role in the attachment to surfaces
Axial Filaments Found only on
spirochetes
Axial Filaments cause
entire cell to rotate for moility
Anchored at one end of cell, like flagella (structurally), but wrapped around
cell
Axial Filaments
What are Structures Internal to the Cell Wall
of Bacteria?
Ribosome -Nucleoid
Storage granules (cytoplasm)
Single membrane bound vesicles (Plasma membrane )
Cytoplasmic membrane
Ribosome of bacteria is Located in the
cytoplasm
Gives bacteria a granular appearance in electron micrographs
Ribosome
Ribosome Function
Translates mRNA into protein.
Location of the bacterial genetic DNA
Nucleoid
Storage granules Storage of nutrients in the
cytoplasm
Storage granules in bacteria is Composed of
glycogen, sulfur, or polyphosphates
Caused by increased osmoic condiions
Single membrane bound vesicles
Rapid lose of water causes
the Plasma membrane to pull away from
cell wall which allows the membrane to have a smoother appearance.
Cytoplasmic membrane Made of
phospholipids with proteins embedded
Cytoplasmic membrane function
It maintains the selecive permeability of the cell ( gate for in and out things)
During cell division the chromosome is linked to cell membrane at a site
called
mesosomes
Semi-rigid structure which gives cell its’ shape
Cell Wall
what is the Cell Wall
Funcions ?
Functions to protect the cell from Osmotic pressure and serves as an
attachment point for flagella
peptidoglycan is only found in the
cell walls of bacteria
Cell Wall Contains porin for what?
To transport of low molecular weight substances.
What is the diference between gram positive bacteria and gram negative bacteria?
Gram positive bacteria have a thick peptidoglycan layer and
no outer lipid membrane, whilst Gram negative bacteria have a
thin peptidoglycan layer and have an outer lipid membrane
have antigenic properies and can be used to identify Gram posiive bacteria
by serological tests
Teichoic acids
endotoxin in Gram Negative
Lipopolysaccharide (LPS)
Outer membrane of Gram Negative is composed of
phospholipids and lipopolysaccharide
Lipopolysaccharide (LPS) determines
determines antigenicity (O antigen) and pathogenicity
Gram Negative
Consists of an
outer cell membrane and the periplasmic space
Periplasmic space in Gram Negative
contains
lipoprotein and peptidoglycan layer
✅❌
Fruits and Vegetables have natural
micro-flora on their surface
and can become contaminated with foodborne pathogens
✅
Examples of natural micro-lora on their surface
Bell peppers > Listeria
Corn > Enterococcus
Garlic > Leuconostoc Cucumber Lactobacillus Grapes > Leuconostoc
Examples about Fruits and Vegetables can become contaminated with foodborne pathogens
Sprouts > Salmonella Letuce > Listeria monocytogenes Apples > E. coli O157:H7 Cantaloupe > Salmonella Cabbage > Listeria monocytogenes
Air can contain Molds,viruses and bacteria
Levels in the air depend on:
- Humidity ( high more Microorganisms)
- Size and level of dust paricles
- Temperature (opimum and minimum)
- Resistance to drying
is rich source of microorganisms
Soil
Bacteria spore formers
Clostridium, Bacillus
fungal spores produced by
Aspergillus
(soil speciic)
Enterobacter
Water can be contaminated with
Pseudomonas,
Klebsiella,
Vibrio,
E. coli
Wash water (municipal water) may contain
103 psychrotroph /ml
are known contaminates of dairy product
Bacteria that are found in the intesinal tract
E. coli
Animal hides, skin & hair contain
Staphylococcus
How can Shellish bed contaminaion ?
- Improperly treated sewage
2. Pathogens naturally found in waters such as Vibrios
life cycle of biofilms
1-reversible atachment 2-Irreversible atachment 3-Early development of biofilm formaion 4-Maturation 5-Dispersion
Bacterial cells are released from biofilms into the surrounding environment.
Dispersion
Maturation the biofilm
the biofilm develops into an organized resistant structure to chemicals and disinfectants.
Initial reversible attachment Biofilms formation starts with the
attachment of bacteria to solid surfaces mainly due to van der Waals and electrostaic forces.
Irreversible attachment
The biofilm grows through cell division and irreversible atachment with producion of extracellular polymers substance (EPS) .
The EPS layer strengthens the structure between bacterial cells and atachment surface.
Early development of biofilm formation
what is the Biofilms ?
as a community of bacteria enclosed in a self-produced
exopolysaccharide matrix that adheres to a biotic or abiotic surface.
is the physical movement or transfer of harmful
bacteria from one person, object or place to another
Cross contamination
Cause miscarriage in pregnant women.
Listeria monocytogenes
Thermophilic 🦠bacteria
are those that can grow at high temperatures
which are normally found in hot springs.
Psychrotrophic bacteria 🧫
are those that can grow at refrigeraion temperatures and lead to the spoilage of product.
