Difference Between Oomycetes and True Fungi

The key difference between oomycetes and true fungi is that oomycetes have cellulose, beta-glucans, and hydroxyproline in their cell wall while true fungi have chitin in their cell walls. Another major difference between oomycetes and true fungi is that somatic thallus of oomycetes is diploid while somatic thallus of true fungi is haploid.

Oomycetes and true fungi are two groups of eukaryotic organisms that show filamentous growth. They also feed on decaying matter. But the cell wall of oomycetes is made up of cellulosic compounds and glycan. They do not have chitin. True fungi have chitin in their cell walls.

CONTENTS

1. Overview and Key Difference
2. What are Oomycetes
3. What are True Fungi
4. Similarities Between Oomycetes and True Fungi
5. Side by Side Comparison – Oomycetes vs True Fungi in Tabular Form
6. Summary

What are Oomycetes?

Oomycetes resemble fungi, but they are pseudo-fungi.  They used to be called lower fungi. However, they are more like protists such as brown and golden algae and diatoms. Oomycetes are also called water moulds. They are filamentous and show filamentous growth as well. They are mainly terrestrial and aquatic eukaryotic organisms. Some oomycetes that are saprophytes feed on decaying matter and obtain nutrients via absorption. However, many are pathogenic.

Cell walls of oomycetes have cellulose, beta-glucans, and amino acid hydroxyproline. They do not have chitin in their cell wall, unlike true fungi. Another key feature that separates oomycetes from true fungi is that oomycetes have diploid nuclei. They also have tubular cristae in mitochondria. Oomycetes’ sexual reproduction occurs via oogonia while asexual reproduction occurs by the formation of a structure called sporangia.

Terrestrial oomycetes are parasites of vascular plants. They cause plant diseases such as root rot diseases of a wide range of plants, foliar diseases of many plants, seed rot and pre- and post-emergence seedling death, late blight of potato and tomato, stem rots of many plant species, etc.

What are True Fungi?

True fungi are a member of Kingdom Fungi. Their cell walls contain chitin. They are eukaryotic and filamentous organisms. They can be unicellular (Yeast) or multicellular (Penicillium, Aspergillus, Colletrotricum, etc.). Moreover, they form hyphae like structures. Their hyphae can be septate or aseptate. A collection of hyphae is called a mycelium. Fungi show heterotrophic nutrition pattern. They can also reproduce sexually via gametes and asexually via spores.

Fungi have both beneficial and harmful effects. Fungi such as Penicillium are useful during antibiotics production. Some fungi are edible (mushrooms). Some fungi produce secondary metabolites such as vitamins, enzymes and hormones. Unicellular yeast is very important in many industries such as wine industry, bakery industry and the dairy industry, etc. In contrast, some fungi are very harmful and pathogenic and cause diseases to both humans and plants.

What are the Similarities Between Oomycetes and True Fungi?

• Oomycetes are a group of lower fungi that resemble true fungi.
• Both are filamentous and microscopic.
• They are eukaryotic organisms containing a nucleus and membrane-bound organelles.
• They are saprophytic or pathogenic.
• Both types are not photosynthetic organisms.
• They cause diseases in plants and animals.
• Some oomycetes and true fungi act as bio-controlling agents.
• Moreover, they can reproduce via both sexual and asexual methods.

What is the Difference Between Oomycetes and True Fungi?

The key difference between oomycetes and true fungi is that oomycetes are lower fungi that do not contain chitin in their cell wall while true fungi have chitin in their cell wall. Another major difference between oomycetes and true fungi is that oomycetes bear a diploid somatic phase while true fungi have haploid somatic phase. Moreover, oomycetes have tubular mitochondrial cristae while true fungi have plate-like mitochondrial cristae.

Below infographic summarizes the difference between oomycetes and true fungi.

Summary – Oomycetes vs True Fungi

Oomycetes are filamentous fungi-like eukaryotic organisms which are known as water moulds. Though they resemble fungi, they are not fungi. They do not contain chitin in their cell walls. Moreover, they have diploid nuclei within their filaments. True fungi are members of spore-producing eukaryotic organisms that belong to Kingdom Fungi. Common fungi include yeast, moulds and mushrooms. They have chitin in their cell walls. Moreover, they have haploid nuclei within their filaments. So, this is the summary of the difference between oomycetes and true fungi.

Reference:

1. “Introduction to the Oomycota”, UC Museum of Palaeontology, Available here.

Image Courtesy:

1. “Phytophthora reproduction” De la (Reproduced courtesy of Matteo Garbelotto, UC Berkeley [A, D], and Edwin R. Florance, Lewis & Clark College [Portland, Oregon, United States] and the USDA Forest Service Pacific Southwest Research Station in Albany, California [B, C].) – Nicholls H: Stopping the Rot. PLoS Biol 2/7/2004: e213. https://dx.doi.org/10.1371/journal.pbio.0020213 (CC BY 2.5) via Commons Wikimedia
2. “Fungi collage” By BorgQueen – Sources clockwise from top left: File:Amanita muscaria tyndrum.jpg, File:Scarlet elf cap cadnant dingle.jpg, File:Mouldy bread alt.jpg, File:Spizellomycete.jpg, File:Aspergillus.jpg (CC BY-SA 2.5) via Commons Wikimedia