Manjunatha SI M.Sc. (Botany)

University of Mysore

SYMBIOTROPHES

CONTENTS1.Introduction2.Symbiosis3.Lichens: Mode of Nutrition4.Mycorrhizae: Mode of Nutrition5.Other examples of Symbiotrophes6.Conclusion7.References

INTRODUCTION Symbiosis can be defined as the association between dissimilar organisms in which benefit may accrue to both at least for a period during the association. Associations need not be static. In a few cases, the symbiotic phase may continue to a parasitic or commensal phase.

FUNGI IS SEEN IN MAJORITY OF SYMBIOTIC RELATIONSHIPS…….!!!!!!

Many fungal mutualisms are driven by the ability of the fungus to decompose organic substrates that are inaccessible to its host

EXAMPLES OF SYMBIOTIC RELATIONSHIPS

1.Lichens2.Mycorrhizae3.Termites and Termitomyces (basidiomycete)4.Ambrosia symbiosis5.Gut symbionts 6.Scale Insects and Fungi

LICHENS

Lichen is defined as a ‘self supporting association of a fungus (Mycobiont) and a Green algae or Cyanobacterium (Photobiont), resulting in stable thallus of specific structure’

• Some 13500 species of Lichenized Fungi have been described to date & only 100 species of photobiont is known.

• Most of the lichens do not have the mechanism to absorb nutrients from the soil and they depend on atmospheric sources for nutrients.

Three main types of lichens:

1. Crustose lichens form flat crusty plates.

  2. Foliose lichens are leafy in

appearance, although lobed or branched structures are not true leaves.

3. Fruticose lichens are even more finely branched and may hang down like beards from branches or grow up from the ground like tiny shrubs

NUTRITION IN LICHENS

Hill and Smith(1972) devised simple and elegant method termed the “Inhibition technique” to show the transport of glucose from Photoibiont to Mycobiont

1. Cyanobacterial Photobionts export Glucose to Mycobiont, whereas Green algae export polyols such as Erythritol (Trentepohlia), Sorbitol(Hyalococcus, Stichoccus), Ribitol(Trebouxia, Coccomyxa, Myrmecia) to Mycobiont.

2. Nitrogen fixed by the Cyanobacterium is released to the Mycobiont as ammonium and is incorporated into amino acid pool as Glutamate.

1. In simple, non-stratified crustose lichens, haustoria formed within the photobiont cells.2. In more highly differentiated lichens, haustoria are often reduced to a pad-like infection peg appressed to but not breaking the algal wall Such structures have been called Intraparietal haustoria 

1.The benefits to the photo-biont may include the buffering against adverse environmental conditions such as high solar irradiation. The upper cortex of many lichens is brightly coloured due to the presence of pigments which screen out UV light

2. The fungus provides water and minerals to it.

3. Creates a firm substratum within which the phycobiont can grow & protected from environmental stress.

MYCHORRHIZAE More than 70% of vascular plants are Mycorrhizal, as are many Pteridophytes(ferns & their allies) & some bryophytes especially Liverworts. Mycorrhizae refers to an intimate association between a root and other underground organ and Fungus. Major types of Mycorrhiza are 1. Arbuscular mycorrhiza 2. Ectotrophic mycorrhiza 3. Ericoid mycorrhiza 4. Orchid mycorrhiza 5. Ectendotrophic mycorrhiza

NUTRITION IN MYCORRHIZA It is a Mutualistic association where both get benefittedFungus gains most or all of its organic carbon from Plant, while the Plant obtain mineral nutrition's from soil via Fungal hyphae.

• In Natural and cropping environment, its major role is to supply Minerals mainly the Phosphate, because Phosphate is extremely immobile element in soils.

• But in acidic soils of moorlands and woodlands where the rates of decay of leaf litter are relatively slow, mycorrhizal fungi helps in obtaining Nitrogen by means of their protease enzyme.

TERMITES AND TERMITOMYCES (BASIDIOMYCETE)

In Africa, termites in the subfamily Macrotermitinae cultivate basidiomycetes, much like attine ants. The termites consume plant material and deposit it as fecal material in the nest. Fungi in the nest digest the plant tissue and the termites consume the fungi. Fungal cellulases remain active in the termite’s gut. As in attine ants, females that disperse to found new colonies bring fungal inoculum with them.

AMBROSIA SYMBIOSIS• Its evolutionary mode referred to as Fungal farming.

• More than 3200 known ambrosia beetle species gain nutrition from fungi

• All ambrosia beetles studied to date cultivate Ascomycotan fungi.

• Recently Scientists discovered Ambrosia- Basidiomycotan Fungi association i.e., between Ambrosiodmus-Flavodon

• Ambrosiodmus possessed preoral mycangia containing hyphae.

• Capable of turning rotten wood into complete animal nutrition

AMBROSIA BEETLES, BARK BEETLES AND THE SIREX WOOD WASP

A range of insects that are found in living trees utilize fungi they carry with them to partially digest the timber thus nourishing the larvae. The associations are symbiotic, in that the insect carries the fungus from tree to tree in specific pouches called mycangia, and the fungus digests the food for the insect.

SCALE INSECTS AND FUNGI It involves Septobasidial fungi (Basidiomycota) and scale insects. 1.They form an association in which the insect

relies on the fungus to provide protection from predators, parasites and pathogens.

2.The fungus gains nutrients and a means of dispersal, and appears to rely on the insect absolutely.

GUT SYMBIONTS

Neocallimastix spp. – CHYTRIDIOMYCETES

Found in the stomachs of cows and other ruminant herbivores. Along with bacteria and other microorganisms, these anaerobic fungi help cows digest plant matter.

CONCLUSION1. Lichens are fungi that have discovered

agriculture" — Trevor Goward2. A few fungi have evolved close functional and

structural associations with insects and other organisms. The associations are closely integrated and mutually beneficial. In each case, the fungus appears to be gaining access to organic energy, and in a few systems, the animal ensures close association by dispersing with the symbiont attached.

REFERENCES1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4569427/2. http://bugs.bio.usyd.edu.au/ 3. Alexopoulos and Mims, Introductory Mycology 4th edition4. John webster and Roland weber, Introduction to fungi, 3rd Edition, Cambridge University press5. Presscot, Harley, Klein, Microbiology, 5th Edition 2002, Tata McGraw Hill Company6. https://en.m.wikipedia.org7. www.researchgate.net

THANK YOU