Q1: Fungal growth, evolution, and ascomycota Flashcards
Fungi cause the majority of all known ____ diseases.
plant
Fungi were originally regarded as members of the ____ kingdom.
plant
The “body” of a fungus.
Hyphal thallus
Pleomorphic:
Able to produce several different forms.
A mass of hyphae.
Mycelium
Hyphal strands grow in ____ but not ____.
length; girth
Structures that divide the hyphae of some fungal groups into different cells.
Septa; a septum
Hyphae that lack septa.
Aseptate or coenocytic
Individual cells of septate hyphae may have ### nuclei.
One, two, or many
Fungi grow in a ____ manner.
Radial
Yeasts (do/do not) form a monophyletic group.
do not
(T/F) Fungi grow either as a mycelium or a yeast.
False; some can be dimorphic, changing form depending on environmental or genetic conditions.
(T/F) Fungal spores are produced asexually.
False; can be produced asexually or sexually.
(T/F) Fungal spores are unicellular.
False; can be unicellular or multicellular.
Zoospores:
Aquatic spores that have flagella and can swim in water.
Aquatic spores that are motile.
Zoospores
The two broad ecological categories of fungi.
Saprobes & symbionts
The category of fungi that decompose dead organic matter.
Saprobes
The three categories of parasitic fungi.
Necrotrophs, biotrophs, and hemibiotrophs.
The category of parasitic fungi that kills cells then live as a saprobe in the dead tissue.
Necrotrophs
The category of parasitic fungi that require living cells from which to obtain nutrients.
Biotrophs
The category of parasitic fungi that initially require living cells, but then act as necrotrophs.
Hemibiotrophs
Dimorphic
Capable of growing as mycelium or yeasts.
Fungi release ____ into their local environment to break down complex structures.
extracellular enzymes
Sessile:
Stationary
Fungi utilize ____ growth to continuously extend into new zones of substrate.
apical
As the apex extends, the protoplasm is pushed toward the tip by ____ that form and expand in the older parts of the hyphae.
Vacuoles
As the apex expands, older zones of hyphae become _____.
Metabolically inactive
(T/F) Fungi can synthesize enzymes specific to the substrates they encounter.
True; specific enzymes are not always present and synthesis may be induced by the availability of a substrate.
The process by which fungal enzyme synthesis can be triggered by environmental conditions.
Enzyme induction
The process by which fungal enzyme synthesis can be prevented by the presence of an alternative preferred nutrient source.
Catabolite suppression
The process by which fungal enzyme synthesis can be prevented in response to environmental conditions.
Enzyme suppression
The methods by which fungi limit the ability of other organisms to share in the nutrients that break free from a substance.
(1) Feedback mechanisms that match enzyme synthesis to the rate at which breakdown products are used, (2) final stages of substrate breakdown being performed by wall-bound enzymes, and (3) producing antibiotics or other growth-suppression metabolites.
Hyphal wall materials are transported to the apex by ____.
vesicles
____ pressure causes the apex tip to extend forward in growth.
Turgor
Some species of xerophytic fungi can extract water vapor from the air or a dry substrate by _____.
generating low hyphal water potentials
Most fungi grow well in the temperature range ____.
10-30C
Fungi capable of growth at very low temperatures.
Psychrophiles
Fungi capable of growth at very high temperatures.
Thermophiles
Fungi that can optimally grow at a range of 10-30C.
Mesophiles
How do thermophiles maintain membrane fluidity at high temperatures?
Having more saturated fatty acids in their membranes.
How do psychrophiles maintain membrane fluidity at low temperatures?
Having more unsaturated fatty acids in their membranes.
The two requirements for extremophile fungi to live at extremes:
(1) Maintain membrane fluidity and (2) maintain synthesis of functional proteins.
Fungi whose growth is reduced markedly if the partial pressure of oxygen drops much below that of air.
Obligate aerobes.
Fungi that grow well in an oxygenated environment, but can also in the absence of oxygen by fermentation of sugars.
Facultative aerobes.
Fungi that are aquatic and have only rudimentary mitochondria and low cytochrome content. They can grow in the presence or absence of oxygen, but only by means of fermentation.
Obligately fermentative fungi
Fungi that are killed upon exposure to oxygen.
Obligate anaerobes.
Fungi generally prefer environments in which the pH is slightly ____.
acidic
Zonate growth in culture is believed to be due to _____ of surface hyphae.
light inhibition
In some fungi (Pilobolous), light triggers formation of ____ which subsequently grow towards the light.
sporangiophores
Phototropism
The ability to sense and grow in response to light.
The approximate number of described fungal species.
100,000
The estimated number of total fungal species.
1.5 million
Ultrastructural morphology:
Morphology examined at the cellular and subcellular level.
Common ultrastructural morphological structures used for classification include:
(1) Flagella, (2) septa, (3) mitochondria, and (4) ploidy level.
Biochemical classification characters include:
(1) Cell wall components, (2) amino acid synthesis pathways, (3) sterol synthesis pathways, (4) ability to break down different C substrates, and (5) production of secondary metabolites.
Most fungal evolutionary work has been done with ____ or ____ DNA.
nuclear; mitochondrial ribosomal
The main four characters of fungi:
(1) Chitin in cell walls, (2) primarily haploid life cycle, (3) glycogen is used as main storage product, and (4) mitochondria with plate-like cristae.
rDNA
Ribosomal DNA
Cryptic species
Species that are very closely related and (nearly) morphologically identical, but genetically or ecologically distinct.
Species that are very closely related and (nearly) morphologically identical, but genetically or ecologically distinct.
Cryptic species
Which two phyla encompass ~98% of all described fungi?
Ascomycota and Basidiomycota
The monophyletic group that includes both Ascomycota and Basidiomycota.
Dikarya
What is a dikaryon?
A hyphae with two nuclei that arises from gamete fusion (mating) that is not directly followed by nuclear fusion.
Ascomycota encompasses ~____ of all described species.
2/3
Members of Ascomycota are distinguished by the formation of _____ in a _____.
sexual spores; sac-like cell called an ascus
The primary defining morphological feature of Ascomycota.
The ascus
Mature spores of the phylum Ascomycota.
Ascospores
Ascomycota: septate or aseptate?
Septate; contain “simple” septa
The life cycle of Ascomycota members is predominated by the ____ stage.
Haploid (n)
Plasmogamy
The fusion of gamete structures during sexual reproduction that gives rise to the dikaryotic (n+n) stage.
Karyogamy
Nuclear fusion that occurs within the ascus mother cell to form a diploid (2n) zygote.
The ascus mother cell is ____.
Dikaryotic (n+n)
The zygote in Ascomycota is _____.
Diploid (2n)
In Ascomycota, meiosis occurs in the _____.
Zygote
Ascospores are produced by the _____.
Zygote
Asexual spores are called _____.
Conidia
Conidia
Asexual spores
Conidia are produced during the _____ life cycle.
Haploid
Homothallic
Not requiring differential mating strains to complete sexual reproduction.
Heterothallic
Requiring different mating strains to complete sexual reproduction.
The subphylum within Ascomycota that contains general that appear only distantly related to each other, contains unicellular soil-inhabiting saprobes, dimorphic genera (saprobic yeast, parasitic hyphae), and only a single genera that produces multicellular fruiting bodies.
Taphrinomycotina
Taphrina:
Genera of fungi parasitizing vascular plants (i.e. Peach Leaf Curl). The dikaryotic mycelium is not purely reproductive, but also assimilative.
The subphylum within Ascomycota that is a well-supported monophyletic ground, contains yeasts and hyphal thalli, and all members lack any sort of multicellular specialized structures to protect the asci (the asci are “naked”).
Saccharomycotina
Saccharomyces:
The yeast most well-known for its role in baking and brewing. Its natural habitat is on the surface of fruit.
