Fungi in phylogenetic context, history of mycology, hyphae

systematics

identification, taxonomy, and nomenclature of organisms, including their classification of living things with regard to their natural relationships and the study of variation and the evolution of taxa

taxonomy

description, identification, nomenclature, and classification

• subset of systematics

what is the hierarchical classification starting from largest

domain, kingdom, phylum, class, order, family, genus, species

• dear king phillip came over for good soup

what is the hierarchical classification for fungi (ending letters)

eukarya (domain), fungi/mycota/eumycota/holomycota (kingdom), mycota (subphylum-mycotina)(phylum), mycetes (class), ales (order), aceae (family)

who is the founding father of mycology

micheli. 1729. first to observe the spores of fungi and understand them as reproductive units.

what are the three fundamental domains of life

bacteria, archaea and eukarya (fungi, plants, animals)

definition of fungus

filamentous eukaryotic heterotrophs with apical growth, distinctive cell walls (composed of chitin, glucans, mannans, and sometimes melanin) and typically have haploid nuclei, although hyphae may contain more than one nucleus (dikaryotic condition)

hyphae

fundamental units of fungal ‘bodies’ AKA ‘the mycelium’

units of dispersal

everything in a fungal body. includes: sexual spores, asexual spores, chlamydospores (thick walled spores), sclerotia (& microsclerotia), vegetative propagation, hyphae

mode of growth of hyphae

exploration(extension) from the ends and colonization/capture/resource exploitation from the middle (also where the spores develop and where we find the oldest hyphae). it’s autotropic and self avoidant

autotropic

growing in a straight or vertical line. describes growth pattern. 

phagotrophy

a form of nutrition where an organisms engulfs and ingests food particles

osmotrophy

a feeding method where organisms directly absorb dissolved organic molecules from their envr

who is the founding father of classification

carl linnaeus. swedish biologist and physician created the modern system of binomial nomenclature for naming organisms.

robert hooke

one of the first scientists to investigate living things at microscopic scales in 1655 using a compound microscope that he designed. he described and illustrated a hairy mold colony (Mucor)

antonie van leeuwenhoek

father of microbiology. observed yeast budding. 1689

mathieu tillet

won the bordeaux prize for deciphering that a fungal pathogen (later named in his honour, Tilletia) was the cause of ‘stinking bunt’ of wheat. 1750

agostino bassi

demonstrated that a fungus, Beauveria, was the causative agent of ‘muscardine disease’ of silkworms (it decimated the silk industry). 1834

Johann lukas schonlein

demonstrated the first fungal ‘germ’ of humans, linking the skin disease favus to trichophyton. 1839

miles joseph berkely

england’s foremost mycologist, was convinced that phytophthora was the causative agent of the potato blight. he was scorned by the scientific establishment of the time, but he was rights (although it’s an oomycete, not a fungus per se) 1840s

heinrich anton de bary

botanist and physician published seminal works describing the rusts of cereals and developing a classification scheme that was largely in use until the advent of molecular systematics. 1852-66

louis pasteur

noted that heating a fermentation of wine removed bacterial cells, leaving yeast to flourish (pasterization). 1854

albert bernhard frank

described mycorrhization, correctly understanding the syndrome as symbiotic. 1855

alexander flemming

noticed that a staphylococcus aureus he was maintaining had become contaminated with a fungal spore and exhibited inhibited growth. 1928

howard walter florey and ernst boris chain

isolated penicillin and fundamentally changed the practice of medicine. 1940-44

henry arthur reginald buller

first professor of botany and geology at the u of m. 1904

what clade are fungi in

opisthokonts, a broad group of eukaryotes which also includes animals

dikarya

a subkingdom of fungi that includes the divisions ascomycota and basidiomycota

non dikarya fungi

mucuromycota, zoopagomycota, olpidiomycota, blastoclaadiomycota, chytridiomycota, aphelida

telemorph

the sexual reproduction stage (morph), typically a fruiting body

anamorph

an asexual reproductive stage (morph), often mold life. when a single fungus produces multiple morphologically distinct anamorphs, they are called synanamorphs

holomorph

the whole fungus, including all anamorphs and the telemorph

rhizomorphs and mycelial cords

dense interwoven strands of hyphae. mycelial cords are larger but functionally the same as rhizomorphs.

what kind of growth do fungi exhibit

apical dominance (polarized growth) - one direction only which allows it to be autotropic (self avoidant)

what is apical dominance mediated by

spitzenkorper body

spitzenkorper

aggregations of vesicles near the tip of hyphae that directs hyphal growth. integral for germination

where does growth and extension occur

throughout a hypha, whereas extension occurs only at the tip

how does individual hypha grow vs a colony

ind hyphal growth rate is linear, while a colony (the mycelium as a whole) grows exponentially

what are the components in the spitzenkorper

macrovesicles (exterior) and chitosomes (interior)

macrovesicles

secretory, contain enzymes and structural proteins (including mannans)

chitosomes

delivery of inactive chitin synthases which become activated when in contact with the phospholipid bilayer of the cellular membrane

where and how are chitosomes and vesicles transported

transported to hyphal apex by actin microfilaments and microtubules (which are closely associated with mitochondria)

how are vesicles transported to the fungal hyphal tip in ascomycota and basidiomycota.

vesicles move from the golgi apparatus to the spitzenkorper along microtubules, then are carried by actin microfibrils to the plasma membrane

what is the structural building block of chitin in fungal cell walls

n-acetylglucosamine

what happens when glucans are cross linked with chitin

they become alkali insoluble

how do cell wall lytic enzymes contribute to hyphal branching

they lyse (weaken) mature cell walls to allow non apical growth

in fungi grown in liquid culture, what may happen to beta glucans

they can diffuse and form mucilage

melanin in fungal cellular structures

protective structure that protects the hyphae from uv degradation

septum

an internal wall that forms within a fungal hypha

mannoproteins

non filamentous glycoproteins located on the outermost layer of the yeast cell wall

name the layers of the fungal cellular structure starting from the bottom

• in the phospholipid bilayer of the cell membrane we have our chitin synthase and our beta 1,3 synthase.

• chitin

• beta 1,3 glucan then beta 1,6 glucan

• and lastly the mannoproteins

septin

type of GTPase, a group of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP). core component of the cytoskeleton.

SepA

specific gene that encodes as essential protein in aspergillus nidulans. it’s a formin type protein (plays crucial role in cytokinesis). governs actin

synchronous mitosis

all nuclei within a hyphal compartment divide at the same time

parasynchronous mitosis

mitosis begins with one nucleus and then progresses to adjacent nuclei in a linear fashion. the adjacent nucleus starts to divide after the first one

asynchronous mitosis

nuclei divide independently of their neighbours in an uncoordinated manner

what is a fungal body (mycelium) composed of

hyphae - tubes or filaments with a chitinous cell wall, compartmentalized by septa

what structure governs hyphal extension in fungi

the spitzenkorper

how does fungal mitosis differ from animal mitosis

fungal mitosis is close or semi-open, with the nuclear membrane largely intact. while animals do open mitosis

does fungal mitosis always coordinate with septation

no. mitosis may or may not occur with septation. daughter nuclei may share the same compartment and not all nuclei divide simultaneously

what are key traits of eumycota

• mycelium of hyphae with chitin walls

• septa compartmentalize hyphae

• hyphal growth directed by spitzenkorper

• closed/semi open mitosis

• nuclei can coexist/divide asynchronously

explain the first step in septum formation

septal band assembly

• proteins form a septal band at the site where the septum will be build

• actin (red): provides structural framework and helps constrict the membrane

• septin AspB (blue): scaffold protein that organizes other proteins

• SepA (green): another actin binding protein involved in cytokinesis

• at this point, the daughter nuclei have already completed mitosis

explain step 2 in septum formation

Septin ring splitting

• the AspB (blue) septin ring splits into two rings:

• one basal (toward the old cell) and one apical (toward the growing tip)

• these flank the actin (red) and SepA (green) rings

• this splitting may trigger actin ring constriction, starting the process of narrowing the membrane

explain step 3 of septum formation

Constriction and septal wall deposition

• the actin (red) and SepA (green) rings constrict, pulling the plasma membrane inward

• at the same time, cell wall material (grey) is deposited in the growing septum

• this builds the septal wall that separates the two daughter compartments

explain step 4 of septum formation

completion

after the septum is fully formed:

• actin, SepA, and the basal AspB ring disassemble (they’re no longer needed)

• the apical AspB ring (blue) persists, possibly to mark the site or stabilize the new septum