ch. 12 Fungi

Question 1

Fungi characteristics

Answer 1

cell type: eukaryote
cell membrane: sterols present
cell wall: Glucans; mannans; chitin (no peptidoglycan)
spores: sexual and asexual reproductive spores
metabolism: heterotrophic; aerobic, facultatively anaerobic (only a few are anaerobic)

Question 2

vegetative structures

Answer 2

-fungal colonies are described as vegetative structures because composed of cells involved in catabolism and growth

Question 3

molds and fleshy fungi structure

Answer 3

• thallus= body–consists of long filaments joined together called hyphae.
• hyphae–can grow to immense proportions, from the tips. contain septa
• septa–walls that divided hyphae into distinct, uninucleate cell-like units= septate hyphae
• coenocytic hyphae–no septa. appear as long continuous cells with many nuclei.
• vegetative hypha–obtains nutrients
• reproductive/aerial hypha–produce reproductive spores

Question 4

yeasts

Answer 4

• nonfilamentous
• unicellular fungi
• typically spherical or oval shaped
• with oxygen–metabolize carbs to CO2 and H2O
• without oxygen–carbs to ethanol and CO2–fermentation used in alcohol and baking

Question 5

budding yeasts

Answer 5

• budding yeasts reproduce via budding; parent cell forms a protuberance, the nucleus divides and one nucleus enters the protuberance, then the protuberance breaks off.
• one yeast cell can produce up to 24 daughter cells via budding
• not all buds detach–they form a short chain of cells called pseudohypha–help invade deeper tissues.
• budding yeasts often divide unevenly

Question 6

fission yeasts

Answer 6

-divide evenly to produce 2 new cells

-

Question 7

dimorphic fungi

Answer 7

• dimorphism= two forms of growth
• mold or yeast
• mold–produce vegetative and aerial hyphae
• yeast–reproduce via budding
• often pathogenic

Question 8

spores

Answer 8

• different from bacterial endospores–help in reproduction rather than protection from environment (bacteria)
• spore type helps to identify different fungi
• formed in sexual and asexual reproduction
• asexual spores–formed by hyphae of one organism; genetically identical to parent.
• sexual spores–result from fusion of nuclei from two opposite mating strains of same species. require two different mating strains so less common; contain genetics from both parents

Question 9

asexual spores (conidiospore)

Answer 9

• produced by one fungus through mitosis and subsequent cell division
• NO fusion of nuclei of cells
• 2 types of spores:
  1. conidiospore/conidium: unicellular or multicellular spore that is not enclosed in a sac. produced in a chain at the end of a conidiophore (penicillin, aspergillus)
  a. arthroconidia–formed by fragmentation of a hypha into a single thick cell (coccidioides)
  b. blastoconidia–formed from buds of parent cell (candida albicans, cryptosporidium)
  c. chlamydoconidium–thick walled spore from roundin and enlargment within hyphal segment (candida albicans)

Question 10

asexual spores (sporangiospore)

Answer 10

• produced by one fungus through mitosis and subsequent cell division
• NO fusion of nuclei of cells
• 2 types of spores:
  2. sporangiospore/sporangium: enclosed in a sac called a sporangium at the end of an aerial hypha called a sporangiophore
• sporangium can contain hundreds of sporangiospores
• produced by rhizopus

Question 11

sexual spores

Answer 11

• results from sexual reproduction.
• 3 phases:
  1. plasmogamy: a haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-)
  2. karyogamy: the (+) and (-) nuclei fuse to form a diploid zygote nucleus.
  3. Meiosis: the diploid nucleus gives rise to haploid nuclei (sexual spores) some of which may be genetic recombinants.

Question 12

nutritional adaptations

Answer 12

• fungi grow better at pH5–too acidic for most bacteria
• most molds are anaerobic; most yeasts are facultative anaerobes
• most fungi are resistant to osmotic pressure–can grow in relatively high sugar or salt concentrations
• fungi can grow on substances with low moisture content–often too low for bacteria
• fungi require less nitrogen
• fungi can metabolize complex carbs like lignin (in wood) that most bacteria cant use for nutrients.

Question 13

telemorphs and anamorphs

Answer 13

• telemorph: fungi that produce both sexual and asexual spores.
• anamorphs: can only reproduce asexually.

Question 14

fungal diseases

Answer 14

• fungal infection = mycosis
• difficult to treat because fungi are related to animals—so cells are similar. If we are targeting fungal cells, it is had to avoid animal cells

-5 groups
   systemic
   subcutaneous
   cutaneous
   superficial
   opportunistic

Question 15

systemic mycoses

Answer 15

-infections deep within body that can affect many tissues and organs

• usually caused by fungi in soil
• spores transmitted via inhalation so the infections usually begin in lungs and then spread
• not contagious from human to human/animal to animal

ex. histoplasmosis, and coccidiodomycosis

Question 16

subcutaneous mycoses

Answer 16

• infections beneath skin
• caused by saprophytic fungi that live in soil and on vegetation
• infection occurs by direct implantation of spores or mycelial fragments into a puncture wound on skin

ex. sporotrichosis

Question 17

cutaneous mycoses (dermatomycoses)

Answer 17

• fungi that infect only the epidermis, hair, and nails
• aka dermatophytes
• secrete keritinase that degrades keratin
• infection transmitted by direct contact from human to human/animal to human or from contact with infected hairs and epidermal cells (i.e. barber shop clippers)

Question 18

superficial mycoses

Answer 18

• localized along hair shafts and in superficial epidermal cells
• prevalent in tropical climates

Question 19

opportunistic mycoses

Answer 19

• generally harmless in normal environment but can become pathogenic in a host who is seriously debilitated or traumatized, who is on broad spectrum antibiotics, whose immune system is suppressed by drugs of by an immune disorder, or who has lung disease.
• ex. pneumocystis (AIDS patients), stachybotrys, mucormycosis, aspergillosis, yeast infections

Question 20

lichens

Answer 20

• lichens are combos of green alga (cyanobacterium) and a fungus but classified as Kingdom Fungi according to the fungi strain in the combo (often an ascomycete
• two organisms are in a mutualist relationship
  - can grow where fungus or algea couldn’t grow alone,
  - often first lifeforms to colonize newly exposed soil or rock
  - some of slowest growing organisms on earth

Question 21

lichen morphology

Answer 21

• 3 morphological types
  
  1. Crustose lichens–grow flush or enCrusted onto substratum
  2. Foliose lichens–leaf like
  3. Fruticose lichens–have finger-like projections
• lichen thallus forms when hyphae grow around algal cells to become the medulla. Hyphae project below the thallus to form rhizines or holdfasts. Hyphae also form a cortex of protective covering over the algal layer. Once it becomes a lichen thallus, the alga continues to grow and growing hyphae can incorporate new algal cells.
• lichens incorporate cations into their thalli–can be used to assess the types of cations in the atmosphere by chemical analysis.
• They can also be used to determine air quality due to presence or absence of lichen as air pollutants (especially sulfur dioxide–acid rain) cause death to sensitive species