Lecture 9 Bacteria_ Viruses_ and Fungi

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					Lecture 9: Bacteria, Viruses, and Fungi
BSCI 124

                              Bacteria and Viruses
Viruses
Technically non-living since they can not self-replicate
Consists of just a protein coat for protection and a nucleic acid (RNA or DNA) for
                information
Cellular parasite- uses cell machinery of a host cell to replicate and so produce more
viruses
Cause numerous diseases
         a. examples of human viruses: herpes virus, hepatitis virus, rabies,
                ebola, influenza,HIV (AIDS)
        b.Examples of plant viruses:
                tobacco mosaic virus, wheat stunt virus

Prokaryotes-Bacteria
Unicellular
Prokaryotic-No internal organelles
Haploid (n) only
Replication is asexual- clonal
        -pseudo-sexual reproduction involves transfer of DNA
Forms:
        - cocci, bacilli, spirilli
        -some photosynthetic forms- called cyanobacteria
        -related prokaryote called archae (formerly archaebacteria)- higher form
                         -found in extreme environments of hot springs, salt lakes
Significance
        animal pathogens
        -old scourges: Typhoid, Bubonic Plague, Tuberculosis, Botulism
        -current scourges: syphilis, gonorrhea, E. coli, Salmonella,
                Staphococcus, Streptococcus
        -plant pathogens:
                         rotters, leaf spots
        - beneficial: N 2 fixation, rotters, intestinal bacteria
Control
        -chemicals:
        -nonspecific disinfectants
        - specific antibiotics- some compound that will stop bacterial growth but
                                   not animal growth
                -low or high temperatures
                -low oxygen
                                         Fungi
Eukaryotic organisms NOT plant or animal that can grow on countless substrates

Heterotrophic – depend on external sources of organic material for food
              They have absorptive nutrition by enzymatic help

Size:   small – yeast, mold
        Large – mushrooms, puff balls, bracet fungi

Have cell walls (chitin, cellulose)

Hyphae – treadlike, usually branch extensively
              Septate – have divided cross walls
              Non-septate – no cross walls

Mycelium – collective mass of hyphal filaments

Dikaryons -- hyphae with septa with 2 genetically different nuclei in each cell

Reproduction: (sexual = perfect, asexual = imperfect)
              Spore – break up of hyphae or by specialized fruiting bodies
                     Present in high numbers in the air (ie. Mushroom) unless covered
                                     by ice or snow
                     Can be dormant

Plant Diseases with Major Human Impact
Major impact on society and even changed human history
       70% of all major crop disease caused by fungi
                     ie. Potato famine, brown spot of rice

Late Blight of Potato
Potato major food crop, very susceptible to disease
Phytophthora infestans – potato blight of Ireland 1840s
                      Infects host tissue – causes rapid death of plant parts
                      Hyphae grow out the plants stomata, blow to next plant (low
                              Temp., high humidity)
                      Spread to a whole field in days
Can use fungicides on the fields but this has its positives and negatives
       Rather use integrated pest management – sanitation, crop rotation, biological
                      Controls, disease forecasting, and genetic engineering resistance
Rusts – bread
Basidoiomycetes
Attack seed plants like cereal crops, coffee, apple and pine trees
Causes reddish lesions
Known during the Greek and Roman times
Lack of fruiting body, therefore generally asexual spores that will have multiple life
       stages that will have 2 separate hosts
Most effective control is to use resistant varieties of a plant (done through plant breeding)

Corn Smut
Smut fungi – losses of grain crop by Ustilago mayolis
Only 1 host involved and only 2 spore stages
More common on sweet corn
Forms galls on any above ground part but especially bad on the ear (=total crop loss)
Some people eat the galls as a delicacy

Dutch Elm Disease
The dutch elm was a popular shade tree in Urban areas
Some fungi are more destructive to native forests and ornamental trees (Chestnut blight
80% American trees are dead!)
Ophiostoma ulmi – causes Dutch Elm Disease by vascular wilt (no water can get to parts
of the tree)
Spread by insects (elm bark beetles) by eggs that are infected by the spores
The only thing that can be done is to use varieties that are resistant

Plant and Fungus = Money: Enology

Enology—wine making
Egyptians, Greeks, Romans  Europe

Louis Pasteur – determined yeast on grape skin was responsible for fermentation
(anaerobic) if aerobic = vinegar!

Best Grape: Vitis vinifera vines can produce for 40-50 years, native to the Caspian Sea

Harvest – fall when sugar concentration is high (white grapes must be harvested earlier)
               The % juice and organic acid makes a wine more sweet or more tart

Crush and Pressed

Fermentation – add sulfer dioxide (decreases natural yeast and oxygen)
              Add Acetobacter spp.
              Add correct temp

Clarification – get rid of murky color, sediment by adding clarifier (clay, egg white,
gelatin), then filter
Aging and Bottling


Fungi and Human Health

Secondary metabolites – antibiotics or toxins

Penicillin
Mycotoxins – fungal toxins formed by hyphae, produced in contaminated foods
              Ergot of Rye (Ergotism) – LSD, Salem Witch trials
              Toad Stools-- Alice in Wonderland, hallucinogenic fungi

				
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