General Characteristics Of Microorganisms Flashcards
Yeasts size
5-12u
Bacteria size
1-2u
Molds reproduction
Slow asexual-spores
Sexual cycle
Yeasts reproduction
Intermediate budscars-limit
Sexual-ascus
Zygote
Bacteria reproduction
Fast binary fission
Infinite
Mold diversity
High
Yeast diversity
Moderate
Bacteria diversity
High
Molds substrate utilization
High
Yeast substrate utilization
Low
Bacteria substrate utilization
Highest
Molds pH
Acid tolerant 3-8
Yeasts pH
Acid tolerant 4-8
Bacteria pH
Neutral 5-10
Molds oxygen
Aerobic
Yeast oxygen
Facultative( growth oxygen or without oxygen)
Bacteria oxygen
Aerobic-anaerobic
Molds moisture tolerance
Very dry
Yeasts moister tolerance
High level of water
Bacteria moisture tolerance
High level of water
Molds food spoilage
Low pH foods dryer foods( bread and juice
Yeasts food spoilage
Low pH foods high H2O content
Bacteria food spoilage
neutral pH foods high H2O content
Molds size
5-12 u dia , up to 25u length
Fungi are an equally important group
of microorganisms in food microbiology
fungi are used 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
plants, humans, or other animals. Other important fungal activities include the decay of complex plant and animal remains or environmental pollutants.
Fungal pathogens cause
Fungal pathogens cause
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.
Molds
are filamentous fungi
The individual filaments called
hyphae and the mass of these filaments is termed a mycelium
mycelium
is a multinucleate mass of cytoplasm enclosed within a rigid, branch system of tubes
mycelium
These tubes represent a protective structure that is homologous to a cell wall of a unicellular organism.
A mycelium usually arises
from the germination and outgrowth of a single reproductive cell, or spore
Upon germination
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
septa
are usually perforated and allow passage of cytoplasmic fluid and even nuclei between different parts of the hyphae.
yeast are
nicellular 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).
fungi
eukaryotic
fungi reproduce
by both sexual or asexual means, but in either case spores are usually produced.
Sexually produced spores
are derived from the nuclei of parental cells
the parent and the spores
haploid
Two nuclei from the parental cells fuse to form
diploid zygote nucleus
Haploid spore nuclei are derived from
reductive nuclear division (meiosis)
most common habitat of Molds
habitat is soil and spores are widely dispersed in dust.
Physiologically fungi
more adaptable to severe environmental stress than other microorganisms
fungi more adaptable to
They are more tolerant to osmolarity extremes (osmophiles spoil syrup and jams), pH (acidophiles - acid tolerances range within strains or species from pH 1.8 to 8.0), and drying (xerophiles - some can grow at aw
Molds are strictly
aerobic (discuss Ca2+ lactate on cheese) but Yeasts can utilize sugars such as glucose anaerobically (fermentation) or aerobically (respiration)
under anaerobic conditions yeasts
the major end products of yeasts are ethanol and carbon dioxide via the alcoholic fermentation
under aerobic conditions yeasts
complete oxidation of glucose by yeasts accumulates acids, alcohols, esters, glycerol, aldehydes and other products.
Fungi exhibit a wide growth temperature range
but 20 to 30oC is optimal for most species
Some fungi can grow at
0oC and a few thermophilic molds grow as high as 62oC.
