Brief presentation on the general characteristics of Slime mold Dictyostelium and Fungi Allomyces.

1. Eukaryotic Microbiology
Assignment
Topic: General characteristics of Dictyostelium and Allomyces
Submitted to:
Dr. Renna Josephine
Presented by:
Suby Mon Benny (20LS601032)

2. What is Dictyostelium?
• Dictyostelium is a genus of single- and multi-celled
eukaryotic, phagotrophic bacterivores.
• They belong to Kingdom Protozoa, Sub kingdom
Myxomycota and Phylum Dictyosteliomycetes
comprising 46 species in four genera.
• Discovered in 1869 by Brefeld.
• The best known example is Dictyostelium.
• It is so named because the stalk of its multicellular
sorocarp appears as a network.
• This group was initially considered to be fungi. But they
have been included in the kingdom Protista.

3. Where are they found?
• Commonly found in-
• In soil
• On decaying plant materials
• On dung
• They can be grown on non-nutrient agar.

4. How do they reproduce?
• Each spore from a sorocarp germinates to give rise
to one uninucleate haploid amoeba which feeds
by phagocytosis of bacteria.
• Amoebae reproduce asexually by division to form
two haploid daughter amoebae.
• Pseudoplasmodium
• When there is a shortage of food, the individual haploid
amoebas of a cellular slime mold aggregate into a mass
of cells.
• It typically contains many thousands of individual cells.
• The ability of dictyostelium to aggregate into
multicellular slug has given them the name Social
Amoeba

5. Why are they special?
• Most of its genes are homologous to human genes. Therefore D.
discoideum is used as a model organism. It is used to study cell
differentiation, chemotaxis and apoptosis.
• During slug formation, some cells become “sentinel cells” and
vanquish harmful bacteria.
• A 2011 report in Nature published findings that demonstrated a
"primitive farming behaviour" in D. discoideum colonies.

6. Allomyces
• According to traditional taxonomy, Allomyces
is a member of the Blastocladiales in the
Chytridiomycota (chytrids), one of the four
major phyla of Fungi.
• It was discovered in India by British mycologist
Edwin John Butler in 1911.
Occurrence
They are mostly isolated from soils in tropical
countries, commonly in ponds, rice fields, and
slow-moving rivers.

7. Thallus organisation
• They are polycentric and the thallus is
differentiated into a trunk like portion
which has rhizoids below whilst
branching above, often
dichotomously and bearing sporangia
of various kinds at the tips of the
branches.
• Cell is walled with chitin.

8. Life cycle
• Gametothallus
• Homothallic, produce both male and female
gametangia.
• Gametes are unequal in size.
• Primary phase structure is Meiozoospores.
• End phase structure is Anisoplanogametes.
• Sporothallus
• Produces two types of sporangia.
• Meiosporangia
• Mitosporangia

9. Taxonomy
• Emerson in 2011 delineated three subgenera:
• Euallomyces
• Cystogenes
• Brachyallomyces

10. References
• Willey, Sherwood, Woolverton; Prescott’s Microbiology; Mc Graw Hills
Education; 10th edition; Pg.: 569-570, 588.
• Webster, Weber; Introduction to Fungi; Cambridge University Press;
3rd edition; Pg.: 41-45, 153-160.
• https://en.wikipedia.org/wiki/Allomyces
• https://en.wikipedia.org/wiki/Dictyostelium#:~:text=Dictyostelium%2
0is%20a%20genus%20of,known%20as%20%22slime%20molds%22