You might have noticed that moss looks and acts differently than most other plants that you know of. Does this mean moss isn’t a plant? Is it a bacteria? What about a fungus or some type of algae?
Moss is not a bacteria, fungus, or algae but rather a non-vascular plant. It belongs to the division Bryophyta which falls under the kingdom Plantae. The domain of bacteria forms a domain of its own that includes prokaryotic organisms. Fungi and Algae each belong to their own separate kingdoms.
Let me help break that down for you in case you’re not remembering much from your college biology 101.
Is moss a bacteria?
The question of whether or not moss is a bacteria is a question about taxonomy (how do we classify moss and group it with other species of plants/animals/living things).
Classifications are broken into taxonomic ranks, with each rank grouping together smaller ranks below it (like branches on a tree).
The highest taxonomic rank is called a domain. There are three domains:
- Archaea – prokaryotic microorganisms
- Bacteria – also prokaryotic microorganisms, but whose cell walls are composed of a complex of proteins and sugars instead of polysaccharides.
- Eukarya (sometimes grouped into Archaea) – living things whose cells have a nucleus
Moss would fall under Eukarya since its cells do have a nucleus. So right off the bat, we can say that moss is not a bacteria because its cells have a nucleus. Instead, you could call it a eukaryote.
Within the Eukarya domain, there are six/seven kingdoms (depending on which model you’re using). Some more recent models classify bacteria as a “superkingdom”.
Moss falls under the Plantae kingdom because it is a photosynthetic eukaryote. So moss is not a bacteria, but rather a plant. In fact, all plants are not bacteria because they fall under the eukarya domain instead (they all have cells with a nucleus).
Within the plant kingdom, there are a number of different divisions. Moss belongs to the Bryophyta division along with liverworts and hornworts. The Bryophyta division groups together non-vascular land plants.
Non-vascular plants don’t have xylem or phloem, structures that conduct water and nutrients throughout flowering plants and ferns. That’s one of the key characteristics that make the 12,000+ species of moss distinct from other plant divisions.
What separates moss from the other bryophytes–liverworts and hornworts–is their leaf structures. Moss leaves grow on a thallus, a stem-like structure that doesn’t have a vascular system.
Moss have leafy arrangements around the thallus in a symmetrical pattern whereas liverworts have leaf-like arrangements attached to the stem and hornworts have narrow pipe-like leaf structures.
Why Moss Is Moss Confused With Bacteria?
My guess at why moss might be confused with bacteria is that some people might confuse moss with algae.
Algae also isn’t a bacteria, but one “algae” that is actually a type of bacteria is blue-green algae. Despite the name, it’s actually not a type of algae.
Blue-green algae is another name for cyanobacteria, a phylum of bacteria that obtain energy from photosynthesis.
I’m guessing through several leaps of logic and associations, moss could be mistakenly associated with bacteria this way.
Here’s my other theory: moss grows low to the ground, on rocks, and on trees and doesn’t have obvious foliage like most other plants.
It’s possible that people might believe it’s not a plant, struggle to classify it, and jump to the closest familiar category they can think of: bacteria.
Is Moss an Algae?
Since I did mention moss could be confused with algae, let me clarify the difference between the two here.
Algae is actually an informal term for a diverse group of photosynthetic, eukaryotic organisms that can be single-celled or multicellular.
Since it is an informal term, there’s no definitive definition for what counts as algae, but generally, they don’t have the structures of land plants like leaves or roots and typically live in aquatic habitats. Algae fall under the kingdom Protista.
Similarly, moss is a eukaryote that likes to grow in moist, shady areas and performs photosynthesis. It also doesn’t have the structures of other flowering plants like stems, roots, and water transport structures.
The main difference between moss and algae is in the body structure. While you could argue moss is a simple plant lacking the more complex structures of flowering plants, algae is another level lower on the scale of simplicity.
Moss do have small, simple leaves and rhizoids that they use to hold onto their substrate. Algae don’t have even these simple structures.
The reproductive cycles of algae are also much simpler than moss. While moss reproduce with spores, algae reproduce vegetatively by splitting cells or meeting and fusing with other algae cells.
Is Moss a Fungus?
Another distinction that is worth clarifying is between moss and fungi.
Fungi do have some similarities to moss like growing on some kind of substrate, reproduce with spores, and tend to prefer shady, moist environments. Sometimes they can even have similar colors.
Despite their similarities, fungi form their own kingdom (Fungi), which is entirely separate from the kingdom Plantae where moss belongs.
A key difference between fungi and plants is chitin in their cell walls in place of cellulose. Chitin is a polymer that’s similar to glucose and is also found in the exoskeleton of arthropods.
Fungi are heterotrophs, meaning they acquire food by digesting things (kind of like animals) and they do not photosynthesize. They get their carbon from other organisms for metabolism.
Unlike moss, they rely on their substrate as a source of nutrients while moss anchors itself to its substrate, but doesn’t extract nutrients from it.
This is why you can often see moss growing on concrete and rocks while you wouldn’t ever see a mushroom growing on top of a rock. Unless it’s maybe growing out of a crack that does have some organic matter hidden inside.
To summarize, moss is not a bacteria, fungus, or algae. It’s a plant that belongs to the kingdom Bryophyta. Moss is distinct from hornworts and liverworts due to it’s symmetrical leaf-like structures around the thallus.
Hope that helps clear up any confusion!