What are Saprophytes?
** Examples and Characteristics
Also known as saprotrophs, saprophytes are organisms that obtain nourishment from dead and decaying organic matter especially plant matter.
While several fungi (e.g., mushrooms) are some of the most common saprophytes, it's worth noting that some flowering plants and bacteria also fall under this group.
By breaking down dead and decaying organic matter, saprophytes contribute to nutrient cycling and thus ensure that various substances and minerals are available in the form that other organisms can use.
* The word saprophyte is derived from the Greek words "Sapros" and "Phyton" which means putrid and plant respectively. As such, it's concerned with decaying plant matter.
While animals like vultures feed on dead animals, they are not classified as saprophytes because saprophytes only feed on and break down dead and decaying plant matter.
Here, then, the term saprotrophs are more appropriate when talking about animals like vultures. The term "troth" in saprotrophs is derived from the Greek word "Trophe" which means nourishment.
Examples
As mentioned, saprophyte is an umbrella term used to refer to a number of organisms that feed on dead and decaying organic material (plant matter).
The following are some examples of saprophytes:
Fungi: Fungi and some of the most popular saprophytes. Some examples of saprophytic fungi include molds, mushrooms, yeast, penicillium, and mucor etc.
Bacteria: Some bacteria survive by breaking down various organic matter including those of dead and decaying animals. As such, they are not saprophytes. However, some, like vibrio japonicus (which break down polysaccharide) and some nitrogen-fixing bacteria, are regarded to be saprophytic.
Saprophytic bacteria break down various complex organic compounds like lignin, cellulose, and hemicellulose among others.
See also: Are Bacteria Decomposers?
Flowering plants: While most plants are capable of photosynthesis and can therefore make their own food, some live as saprophytes and therefore obtain their nutrition from dead and decaying organic matter.
Some examples of saprophytic flowering plants include; Ghost plant (Indian pipe), Burmannia and Sebaea.
While some of these plants are capable of photosynthesis, they partially rely on saprophytism and are therefore described as hemisaprophytic.
Algae: Algae include many organisms in the kingdom Protista that are capable of photosynthesis. However, some species, like members of the genus Polytoma, which lack chlorophyll, have been shown to live a saprophytic life.
Characteristics
All saprophytes rely on dead and decaying plant matter for nourishment (partially or fully). While they have some similarities, there are differences between the different types.
The following are some characteristics of the different types of saprophytes:
Fungi
The majority of fungi are saprophytes and thus depend on dead and decaying organic matter for nourishment. Given that fungi do not have chlorophyll, they do not directly need sun energy which is necessary for photosynthetic plants.
For this reason, they are often found in shady areas (e.g., underneath trees and other vegetation) where dead and decaying vegetation (such as leaves, fruits, fallen branches, and stem, etc.) are.
Compared to these fungi, some are parasitic and therefore depend on a living host (plant or animal). As they obtain their nourishment from these hosts, they can cause damage or disease (cause harm to the host).
The following are some of the main characteristics of saprophytic fungi:
Eukaryotic - Fungi are eukaryotic organisms and are therefore characterized by a complex cellular organization (with membrane-bound organelles). While some of the fungi are single-celled organisms (e.g., yeast), others like mushrooms are multicellular and thus consist of different specialized parts (e.g., hyphae, stalk, cap, etc.)
Lack chlorophyll and non-vascular - Unlike most plants and some organisms that have chlorophyll for photosynthesis, fungi do not have chlorophyll and are therefore unable to make their own food. Because they cannot manufacture their own food, they have to rely on organic matter in their surrounding for nourishment.
Apart from lacking chlorophyll, multicellular fungi are also non-vascular and therefore do not have a vascular system (phloem and xylem) that transports water and nutrients in plants. Instead, they may have in place highly branched filamentous structures known as hypha and mycelium which are involved in the absorption of nutrients.
Enzymes - In order to absorb nutrients from plant organic matter, saprophytic fungi produce various enzymes that act on and degrade various molecules. There are many types of fungal enzymes including cellulase, phytase, lipase, and xylanase among others.
Following the breakdown of compounds (e.g., cellulose and sugars, etc.), required nutrients are absorbed through the hyphae. As the organic matter is broken down further, the mycelium continues to grow over. It can grow on the surface and even penetrate the food source.
Reproduction - Fungi can produce sexually and asexually. Asexually, unicellular fungi like yeast reproduce by budding. Where a bud protrude from the body of the parent cell and ultimately detaches. Multicellular fungi, on the other hand, reproduce by producing numerous haploid spores that divide mitotically to form mature, haploid individuals.
By producing numerous (millions to trillions depending on the fungi) spores, chances of spores landing on a substrate that supports growth are increased. As well, the mycelium can undergo fragmentation and separate into smaller pieces which can then give rise to new individuals.
Under adverse conditions, some fungi can also produce sexually. Here, two nuclei fuse (sex cells) resulting in fertilization and consequently produce a new individual.
Some of the other characteristics of saprophytic fungi include:
· Versatile metabolism - They can break down different types of organic compounds of dead and decaying plants
· Common in dark/shady and moist habitats
· Non-motile - However, mycelium continues to grow in the direction of nourishment
· Can form a symbiotic relationship with other organisms in nature
Based on reproduction, fungi are divided into four main groups that include:
Zygomycetes (e.g., bread mold) - They can be found growing on dead plants as well as on dung. They can produce sexually (through the fusion of zygospores) and asexually through the dispersal of sporangiospores
Ascomycota/Ascomycetes - Ascomycota includes sac fungi some of which are parasitic or coprophilous. However, some are saprophytes or decomposers. They can produce sexually, through the production of ascospores, or asexually through the production of conidiospores.
Basidiomycota/ Basidiomycetes - Basidiomycetes include mushrooms which can produce sexually by producing basidiospores, and asexually through budding and fragmentation etc.
Deuteromycota (fungi imperfecti) - These fungi do not fall into any particular group and sexual reproduction is unknown. However, asexual reproduction is through the production of spores known as conidia.
Saphrophytic Bacteria
As the name suggests, saprophytic bacteria are bacteria that break down or decompose organic matter. In particular, these organisms are capable of breaking down complex compounds like hemicellulose and lignin among others into simpler forms that they can then use or can be used by other organisms.
Apart from saprophytic fungi, saprophytic bacteria are some of the most common organisms found in waste products like kitchen and garden wastes etc. Here, they break down different types of compounds in order to obtain the nourishment they need for survival.
Unlike phytopathogens, which cause damage/disease to plants, some saprophytic bacteria can form a beneficial relationship with plants so that they can benefit each other.
The following are some of the characteristics of saprophytic bacteria:
Unicellular prokaryotes - Unlike fungi, all saprophytic bacteria are unicellular prokaryotes. As such, they are all characterized by a simple cell structure that lacks membrane-bound organelles.
While some fungi like yeast are unicellular organisms, the majority of fungi are multicellular eukaryotes. All saprophytic bacteria, on the other hand, are single-celled prokaryotes.
Enzymes - Like saprophytic fungi, saprophytic bacteria like vibrio japonicus can synthesize a number of enzymes that make it possible to break down various complex compounds.
For instance, studies have shown vibrio japonicus to produce a number of enzymes including carbohydrate lyases, glycoside hydrolases, and carbohydrate-binding module proteins, in carbohydrate-active enzymes like glycoside hydrolases, among others.
Saccharophagus degradans, which is also a saprophytic bacterium produces a number of enzymes including hydrolases, lyases, and esterases through which it's able to degrade such cell components as chitin, cellulose, and pectin, etc.
As the most abundant source of organic compound, the cell wall of plants is an important source of nutrients for different types of organisms.
By producing different types of enzymes that successfully break down this structure, saprophytic bacteria are not only able to obtain nutrients they need for survival, but also make some of the components available for plants and other organisms in nature.
Some of the other characteristics of saprophytic bacteria include:
- Reproduce asexually through binary fission
- Found in soil
- Some saprophytic bacteria can become parasitic under certain conditions (opportunistic parasites)
Flowering Plants (saprophytic flowering plants)
Also known as angiosperms, flowering plants represent the most common and diverse group of all land animals. While the majority of these plants are autotrophs, capable of manufacturing their own food, some obtain part of their nourishment from dead and decaying organic matter. One of the best examples of saprophytic flowering plants is the Ghost plant.
Unlike most plants, the Ghost plant does not have chlorophyll and is therefore incapable of photosynthesis. For this reason, it has been shown to obtain nourishment from decaying matter in very dark areas (e.g., some caves). However, they do not directly obtain nutrients from decaying plants.
Rather, they form a relationship with some fungi which are capable of breaking down dead and rotting matter (e.g., leaves, branches, and tree stumps) to obtain nutrients.
While some of these fungi obtain their nutrition from dead and decaying plant matter, others have a symbiotic relationship with living trees. As the fungi receive nutrients from trees and other plants, the ghost plant (which is a myco-heterotroph) takes these nutrients for its own growth.
For this reason, it's sometimes referred to as a parasite with the fungi acting as the host.
Characteristics of saprophytic flowering plants:
Some of these plants do not have chlorophyll - Because some of these plants lack chlorophyll, they are incapable of photosynthesis. And so, they may appear white in color. However, some may be pink, red, or yellowish in color.
Reproduction - Unlike fungi and bacteria, these flowering plants reproduce through a process known as pollination. The pollen produced in the flowers (anther of the flower) is transferred/transported to the stigma of the same plant (self-pollination) or another plant (cross-pollination).
The pollen (male gametes) then fertilize the ovules (female gametes in the stigma) for fertilization to occur. Fertilized ovules then develop into seeds which can grow to produce new individuals.
Ecology - Because most of these plants do not have chlorophyll, they don't need light energy. As such, they can be found in dark or shady areas (e.g. under the trees, etc.).
Saprophytic Algae
Algae is a large group of photosynthetic organisms that belong to the kingdom Protista. There are few saprophytic algae that belong to the genus Polytoma. Unlike most other algae, these saprophytic algae lack chlorophyll and are therefore incapable of photosynthesis.
For this reason, members of this group rely on dead and decaying organic matter for nourishment.
Some of the main characteristics of saprophytic algae include:
Single-celled eukaryotes - While some algae are multicellular organisms, members of the genus Polytoma are single-celled eukaryotes. As such, they are characterized by membrane-bound organelles. Some of the organelles associated with these cells include an eyespot, contractile vacuoles, as well as a pair of flagella.
* These cells are also characterized by a type of plastid known as leucoplasts as well as a cell wall covering the cell
Ecology - Given that they cannot manufacture their own food, members of the genus Polytoma feed on small water bodies like rainwater pools, etc. that consist of decaying vegetation. Here, they are able to break down these materials in order to obtain the nutrients they need for growth and reproduction.
With regards to distribution, they can be found in different parts of the world.
Reproduction - Saprophytic algae can produce sexually and asexually. Sexually, they produce male and female gametes which fuse to form a zygote that can grow into new individuals. Asexual reproduction, on the other hand, occurs through a process known as zoosporogenesis.
Here, the cell divides to produce four to eight daughter similar daughter cells.
See also:
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References
Ariana Kubartová, Jacques Berthelin, Thierry Beguiristain, and Jacques Range. (2008). Diversity and Decomposing Ability of Saprophytic Fungi from Temperate Forest Litter.
Danièle Gaspard. (2011). Endolithic algae, fungi and bacterial activity in Holocene and Cretaceous brachiopod shells - Diagenetic consequences.
Luana Cassandra. (2014). Saprophytic, Symbiotic and Parasitic Bacteria: Importance to Environment, Biotechnological Applications and Biocontrol.
M. A. Van der Nest et al. (2015). Saprophytic and pathogenic fungi in the Ceratocystidaceae differ in their ability to metabolize plant-derived sucrose.
Links
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/saprophyte
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