Chap2,21,22

Question 1

All of the foods have what?

Answer 1

Microorganisms that are involved in reducing the food Into organic compounds in order to perpetuate the gas and mineral cycle on earth

Question 2

When we discus the relative safety or potencial spoilage of food, we need to focus on two things?

Answer 2

1. What are the total number of microorganisms per gram or ml. 2. What type of organisms are represented on this number

Question 3

If we know what type of organism are associated with plant and animal in their natural state.

Answer 3

Then we can usually predict what microbes are going to be involve into later stages in the processing and the type of spoilage that my occur.

Question 4

In the past, the classification organisms was based upon ?

Answer 4

Numbering taxonomy

Question 5

Taxonomy

Answer 5

Is a system that arranged organisms on the basis of phenotypical similarities and differences among them

Question 6

All of our food originate from where?

Answer 6

Plants and animals

Question 7

Criteria used to classify types of organisms A.

Answer 7

Morphological/gram stain

Question 8

Criteria used to classify types of organisms

b. Biochemical characteristics

Answer 8

• e.g. type of endospore, flagella, and types of substrates utilized.
• This is what the traditional numerical system was based upon. Although this information is still valuable, it is now used primarily to support genetic similarities

Question 9

criteria used to classify types of organisms C. Cell wall composition.

Answer 9

type of peptidoglycan monomer.

Question 10

criteria used to classify types of organisms d. homology between 16S rRNA sequences:

Answer 10

-16S molecule (part of the ribosome) about 1,500 bases long in bacteria

 Because the 16S subunit is an integral part of the ribosome and participates in protein synthesis in all bacteria, some portions of this molecules’ sequence are highly conserved.  Sequence analysis of divergent regions between 16S molecules serves as an excellent measure of bacterial evolutionary divergence.  The subunits are collected and the enzyme reverse transcriptase is used to obtain a DNA version of the molecule for sequencing.  Computer analysis of sequence homology between species is then performed to obtain an estimate of the relationship between organisms.  This technique is so powerful that investigators have been able to identify disease-causing bacteria which previously could not be grown in culture.  This was done by using oligonucleotide primers which anneal to portions of the 16S sequence which are conserved at the kingdom level (e.g. in all prokaryotes) and then use PCR to amplify intervening fragments of the 16S molecules from bacteria present in diseased tissue.  The fragments were then sequenced to identify the dominant bacterium in the tissue.

Question 11

criteria used to classify types of organisms e. Serology;

Answer 11

Serology; cell-wall antigens. e.g. group specific antigens in streptococci.

Question 12

criteria used to classify types of organisms

f. Fatty acid profiles

Answer 12

Ratios of various fatty acids in the cell membrane are characteristic of different species and some microorganisms produce unique fatty acids.

Question 13

criteria used to classify types of organisms g. g. Growth requirements

Answer 13

In discussions of food microbiology, another useful way to group organisms is to consider optimal growth temperatures, oxygen requirements, and particular nutritional requirements or the nutrients that they are able to metabolize. When combined with true taxonomy, this system allows us to identify what species of microbes we need to be concerned about in a particular food product or process. For example, we usually do not need to worry about thermophilic species in refrigerated foods or whether species that require O2 will spoil canned foods.

Question 14

Primary Sources of Microorganisms in Food:One: Soil and Water (Air and dust)

Answer 14

Grouped together because of atmospheric cycling. Soil and water are common sources of important pathogenic and spoilage microorganisms, which is why it is important to thoroughly wash raw foods with good quality water. Air and dust are important sources of microorganisms during food processing and can influence food quality in the home as well.

Question 15

Primary Sources of Microorganisms in Food:2: Plants and plant products

Answer 15

Although most soil and water borne microbes will contaminate plants, very few types actually persist on them. Those that persist, such as lactic acid bacteria and some yeasts, must be able to adhere to the plant material and to utilize it for growth.

Question 16

primary sources of microorganisms in food: 3: food Utensils

Answer 16

another important source for cross contamination of raw and cooked foods e.g. cutting blocks, food trays where raw food was held (BBQ plate).

Question 17

Primary sources of microorganisms in food:4: Intestinal tracts of humans and animals

Answer 17

poor sanitation practices (use of polluted water, poor personal hygiene) lead to contamination from these sources. and many pathogens are transmitted by this route.

Question 18

primary sources of microorganisms in food: 5. Food handlers

Answer 18

microbiota on hands, garments, etc. reflects the habits of the individual. This can include microorganisms from virtually any environmental source

Question 19

Primary sources of microorganisms in food:six: Animal feeds

Answer 19

very important source of Salmonella in poultry and of Listeria monocytogenes (from silage) in dairy and meat animals.

Question 20

primary sources of microorganisms in food: seven: Animal hides

Answer 20

e.g. microbiota of raw milk influenced by that of the udder.

Question 21

Fungi are an equally important group of microorganisms in food microbiology

Answer 21

they are utilized for the industrial fermentation of beer and wine, production of enzymes (e.g. rennet’s for cheese, pettiness to clarify fruit juices and wine, amylases for bread industry, etc), antibiotics, vitamins, and organic acids. The baking industry and the certain types of cheese also depend on fungal activities. Some fungi are pathogens of plants, humans, or other animals. Other important fungal activities include the decay of complex plant and animal remains or environmental pollutants.

Question 22

Fungal pathogens cause about?

Answer 22

70% of all major crop diseases! Some of these outbreaks have been catastrophic:

• Potato blight fungus, Phytophthora infestans, Ireland 1840, 1 million died of starvation, an equal number of people were forced to emigrate to the U.S. or Europe.
• Great Bengal Famine, 1943, 2 million died of starvation due to a severe outbreak of Helminthosporium oryzae on the rice crops.

Question 23

Fungal Morphology:

Answer 23

Molds are filamentous fungi. The individual filaments are called hyphae and the mass of these filaments is termed a mycelium.

Question 24

mycelium

Answer 24

The mycelium is a multinucleate mass of cytoplasm enclosed within a rigid, branch system of tubes. These tubes represent a protective structure that is homologous to a cell wall of a unicellular organism.

Question 25

A mycelium usually arises from?

Answer 25

the germination and outgrowth of a single reproductive cell, or spore

Question 26

Upon germination

Answer 26

the spore puts out a long threadlike hyphae which branches repeatedly as it elongates to form the mycelium. The hyphae of higher molds are compartmentalized by membrane divisions called septa.

Question 27

Septa are?

Answer 27

usually perforated and allow passage of cytoplasmic fluid and even nuclei between different parts of the hyphae.

Question 28

Yeasts are

Answer 28

unicellular fungi that multiply by budding or by binary fission (like many bacteria). Some fungi are dimorphic; they are molds under certain environmental conditions and yeast-like at others (e.g. Candida albicans, M at 20-25oC and Y at 37oC).

Question 29

unlike bacteria, fungi are

Answer 29

eukaryotic

Question 30

fungi

Answer 30

ssexually produced spores are derived from the nuclei of parental cells

Question 31

fungi

Answer 31

in general, the parent and the spores are haploid. Two nuclei from the parental cells fuse to form a diploid zygote nucleus. Haploid spore nuclei are derived from reductive nuclear division (meiosis).

Question 32

Molds:

Answer 32

Most common habitat is soil and spores are widely dispersed in dust.