Language
Country/Area
No result found
Hidden secrets of fungal cell walls: Do you know what semi-starch reaction is?
In mycology, the characteristics and composition of the cell wall are crucial for the classification and identification of fungi. In this context, the concept of "semi-starch reaction" has gradually attracted the attention of scientists. By using chemical reagents such as iodine, the reaction reveals the complex structure and function underlying the fungal cell wall.
"Semi-starch reaction" is crucial for understanding the biological characteristics of fungi and provides an effective tool for checking fungal classification.
Basic concepts of semi-starch reaction
Semi-amyloid reaction refers to the reaction that occurs when fungal cells or tissues contain amyloid polysaccharides when they are tested with an iodine reagent (such as Melz's reagent or Lugol's reagent). This reaction causes a blue to blue-black staining, indicating that certain compounds in the sample have starch-like properties. The name of this reaction comes from the Latin "amyloideus", which means "starch-like". At the same time, negative reactions will also occur, which are called non-semi-starch. Most of these structures remain light yellow to light brown or transparent. Not only microscopic features, such as the outer wall of a spore or the cell wall of a hyphae, take part in this test, but even certain macroscopic features show reactions.
Characteristics of Melz's reagent reaction
Melz's reagent is the main chemical reagent for semi-starch reaction testing. By exposing fungal tissue or cells to this reagent, three color reactions can be observed:
- Starch reaction: The material reacts blue to black.
- Starch-like reaction: The material reacts brown or reddish brown.
- Non-semi-starch reaction: the tissue does not change color or slightly turns to light yellowish brown.
Among these color reactions, two types of semi-starch reactions are worth noting: complete semi-starch reactions and semi-starch reactions. In a complete semi-starch reaction, the sample can be dyed blue without pretreatment with potassium hydroxide (KOH); while when using Lugol's reagent, the sample will appear red after pretreatment with KOH. In some cases, this reaction can even be delayed for up to 20 minutes.
The chemical components of Melz's reagent have their own functions. Chloral water is the main cleaning agent, and iodine is its main staining agent, which promotes the color development of cell walls containing starch galactose.
Biological significance of semi-starch reaction
Semi-starch reaction has important identification significance in the taxonomy of fungi, especially in the category of Ascomycetes. The outer cell wall layer of many ascomycete species exhibits characteristics of a semi-amyloid reaction, reflecting differences in their phylogeny and ecological adaptations.
For example, in two taxa, Lecanorales and Ostropales, the entire outer ascus wall layer may be positive for the hemiamyloid reaction. In the taxon Helotiales, approximately 20% exhibit semi-starch reactions. Although this reaction is an important biomarker for determining species or genus, in past studies, many mycologists chose to use Melz's reagent and ignored the value of Lugol's reagent, resulting in semi-starch reactions. The potential importance has not been adequately appreciated.
Chemical basis of semi-starch reaction
There is still much unknown to the scientific community about the chemical mechanisms of semi-starch reactions. According to some hypotheses, short helical carbohydrate chains alternating with shorter or longer linear segments could lead to this complex reaction. This helical structure of amyloid is able to accumulate in cell walls and in some cases is colored by the action of iodine.
The present experiments show that with the use of iodine reagents, the stretchability of the cell wall is closely related to the structural stability of the ascus, which is an important aspect to further explore the role of semi-starch reactions in fungal biology. This flexibility is particularly required in the area of open pores, where particles can be efficiently pushed out during the release of high cell pressure.
The study of semi-starch reactions will not only help to gain a deeper understanding of the structural characteristics of fungi, but may also become an important reference in future biotechnology or biomedical research.
Taking the above information together, the concept of semi-amyloid reactions provides us with a new perspective on the structure and function of fungal cell walls. This knowledge may change our understanding of mycology. Have you ever wondered how the role of these tiny creatures in the ecosystem may change as our research progresses?
