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Course 6 Microbiology summary
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Test Bank For Brock Biology of Microorganisms 15th Edition By Michael T. Madigan 2024 A+
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Test Bank for Brock Biology of Microorganisms, 15th Edition by Madigan, 9781292235103, Covering Chapters 1-33 | Includes Rationales
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Lesson 1 Microbial diversity: eukaryotic micro-organismsPhylogenetic tree
Indicates how close organisms are related if you compare parts of the genetic codes.
Consists of 3 domains:
1. Bacteria
2. Eukarya
3. Archaea (prokaryotic & unicellular)
Protists
❖ Unicellular eukaryotes
❖ Very diverse group of organisms → many of them are parasites
o Trichomonas vaginalis – STD
o Trypanosoma brucei – sleeping sickness
o Plasmodium – malaria
o Toxoplasma – toxoplasmosis
Group within the protists:
1. Diatoms
- Are phototrophic
- Part of the phytoplankton
- In marine and fresh waters
- Have a cell wall containing silica
2. Oomycetes (water molds)
- Example: Phytophthora infestans
- Causes plant pathogens
- Has caused the potato disease (Irish famine 1845)
- Important for agriculture
3. Amoebozoa
- Pseudopodia causes amoeboid movement
4. Slime molds
- Example: Dictyostelium discoideum
- Can form a colony that works together
- Aggregation, migration, fruiting body formation
Fungi: yeasts and molds
❖ Yeasts and molds are eukaryotic micro-organisms with a cell wall
o Yeasts are unicellular → grow by cell division
o Molds are multicellular → grow filamentous
Yeasts
❖ Unicellular
❖ Divide in different ways
o Cell division (asexual cycle – mitosis)
o Spores (sexual cycle – meiosis)
❖ Example: Saccharomyces cerevisiae. Used in the production of beer and bread
❖ Example: Candida albicans (pathogenic yeast)
1
,Filamentous fungi
❖ Mycelium: network of fungal filaments → these filaments are
called hyphae
❖ Some of the hyphae in the mycelium may not stay on the
surface, they can also be found in the air → called aerial hyphae
❖ In the air, they can form spores → conidia
o Conidia are asexual spores
o Conidia can germinate on their own and form a small hypha
Septum
If you perform a specific cell wall staining, you see that the septa (plural of
septum) are stained whiter than the rest of the cells. Here, you can see the
difference between 1 very long cell, and a filament that contains different cells
Hyphae
❖ Grow from the tip → called apical growth
o Spitzenkörper: place where the hyphae grow (number 11)
❖ Number 2 = septum
❖ They have a continuous cytosol → called coenocytic
Fungal cell wall
❖ Contains of 80-90% polysaccharide
o β-glucan, mannan, galactosan, cellulose
o Chitin: polymer of N-acetylglucosamine (NAG)
❖ PAMPs are parts of the fungus that are recognized by our immune system
Groups within a fungus
Different groups within the fungi:
1. Basidiomycota
2. Ascomycota
3. Glomeromycota
4. Zygomycota
5. Chytridiomycota
Ascomycetes
❖ Important fungi for us
❖ Ascomycetes have sexuals spores in ascus (little bags)
❖ Examples:
Saccharomyces: Aspergillus: Penicillium:
For food production (beer, For food production For food production
bread, etc) and industrial use (cheese) and industrial use and penicillin
2
,Basidiomycetes
❖ Basidiomycetes have basidiospores (sexual spores). Their spores are in the
end of a “stick”, called the basidium
o The basidiocarp is the actual mushroom
❖ Examples:
Agaricus bisporus Amanita muscaria
Reproduction fungi
2 ways to reproduce:
1. Asexual reproduction (mitosis)
- Cell division yeast
- Filamentous growth (cell division)
- Production conidiospores
2. Sexual reproduction (meiosis)
- Sexual spores (ascospores/basidiospores)
Life cycle of S. cerevisisae (unicellular – asexual reproduction)
On the left-hand side, the asexual reproduction is
shown by simple cell division (also called budding) →
haploid stadium. Eventually, you will get a haploid cell
with 1 chromosome.
From this cycle, 2 cells can mate. These yeast cells will
fuse, leaving you with a cell with 2 chromosomes →
diploid cells. By meiosis, it can form an ascus with ascospores. You will then have haploid
ascospores, which can germinate to form the haploid cells
Mitosis
1. Prophase
Replicated chromosomes (2 closely associated sister chromatids)
condense. Outside the nucleus, the mitotic spindle assembles
between 2 centrosomes, which have replicated and moved apart.
2. Prometaphase
The prometaphase starts abruptly with the break of the nuclear
envelope. Chromosomes can now attach to spindle microtubules
via their kinetochores and undergo active movement
3. Metaphase
Chromosomes are aligned at the equator of the spindle, midway
between the spindle poles. The kinetochore microtubules attach
sister chromatids to opposite poles of the spindle
3
, 4. Anaphase
The sister chromatids separate to form 2 daughter chromosomes.
Each is pulled slowly toward the spindle pole it faces. The
kinetochore microtubules get shorter, and the spindle poles also
move apart; both processes contribute to chromosome segregation
5. Telophase
The 2 sets of daughter chromosomes arrive at the poles of the
spindle and decondense. A new nuclear envelope reassembles
around each set, completing the formation of 2 nuclei and marking
the end of mitosis. The division of the cytoplasm begins with
contraction of the contractile ring
Cytokinesis
During cytokinesis, the cytoplasm is divided in 2 by a contractile
ring of actin and myosin filaments, which pinches the cell in 2 to
create 2 daughters, each with 1 nucleus
Meiosis
Importance of fungi
1. Some fungi are pathogenic, causing infectious diseases in human. Those are mainly:
- Superficial infections
- Opportunistic infections (in normal/healthy individuals you usually won’t have a
fungal infection, only if individuals already have an immune system that is
challenged, or in babies)
2. Fungi are important in agriculture and food
- Many fungi are used in food production/fermentation. For example, in the
production of blue cheese/fermented sauces
- In agriculture, plant pathogens are important. When a fungus causes a disease in
a plant, it needs to be eliminated as fast as possible
- The symbiosis between fungi and plants are important, as they can actually help
the plant to grow
3. Fungi are important in the biotechnology
- For example, in the production of enzymes
- They are also important in the biofuel production, to find an alternative for
phosphor fuels
4
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