Glomalin
Glomalin is a hypothetical
Definition and controversy
The specific protein glomalin has not yet been isolated and described.[3] What has been described is an extraction process involving heat and citrate, producing a mixture containing a substance that is reactive to a monoclonal antibody Mab32B11 raised against crushed AM fungi spores. The substance is then provisionally named "glomalin".[4] As many laboratories do not have the equipment to perform an antibody-based isolation (ELISA), a crude mixture called glomalin-related soil proteins (GRSP) is used to refer to the extract portion reactive to the Bradford protein assay. There is significant confusion between the ideal glomalin protein, the antibody-reactive extract portion termed "glomalin", and GRSP.[4]
"Glomalin" was first detected by the Mab32B11 ELISA assay in 1987. According to the scientist that proposed the hypothetical protein, Sarah F. Wright, it eluded extraction until 1996 because "It requires an unusual effort to dislodge glomalin for study: a bath in citrate combined with heating at 250 °F (121 °C) for at least an hour.... No other soil glue found to date required anything as drastic as this."
Description
Based on her extraction, Wright thinks the "glomalin molecule is a clump of small glycoproteins with iron and other ions attached... glomalin contains from 1 to 9% tightly bound iron.... We've seen glomalin on the outside of hyphae, and we believe this is how the hyphae seal themselves so they can carry water and nutrients. It may also be what gives them the rigidity they need to span the air spaces between soil particles."
There is other circumstantial evidence to show that glomalin is of AM fungal origin. When AM fungi are eliminated from soil through incubation of soil without host plants, the concentration of GRSP declines. A similar decline in GRSP has also been observed in incubated soils from forested, afforested, and agricultural land[5] and grasslands treated with fungicide.[3]
It is important to emphasize that glomalin is not synonym of GRSP.
The chemistry of GRSP is not yet fully understood, and the link between glomalin, GRSP, and AM fungi is not yet clear.[3][4] The physiological function of glomalin in fungi is also a topic of current research.[6]
Effects
Glomalin is hypothesized to improve soil aggregate stability and decrease soil erosion.[5] However, since glomalin can not be adequate quantified in soil, studies usually analyze the GRSPs extract, which is a complex mixture including proteins and other substances.[4]
GRSPs, the mixture of proteins and
See also
References
- ^ a b c d Comis, Don (September 2002). "Glomalin: Hiding Place for a Third of the World's Stored Soil Carbon". Agricultural Research: 4–7.
- ^ Comis, Don (October 1997). "Glomalin—Soil's Superglue". Agricultural Research: 23.
- ^ doi:10.4141/S04-003.
- ^ ISSN 0038-0717.
- ^ S2CID 11007821.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - ISSN 0031-4056.
- ^ .
- PMID 21167717.