Effect of Light on Cordyceps militaris Colony Morphology
- Neeraj Kumar
- 17 hours ago
- 4 min read
Cordyceps militaris as the survival tool
Cordyceps militaris is the survival tool for the mankind. Hundreds of research publications, in-vitro, in-vivo and clinical trial studies strengthen it anti-inflammatory (inflammation is the key to most of the diseases/ailments/disorder), anti-viral (HIV, Influenza, SARS, and probably many others), anti-oxidant, immunity booster, bidirectional immunomodulator, anti-aging, anti-tumor, anti-cancer (encouraging data on prevention and treatment of some cancer, also as a potent adjuvant therapeutic agent) and many other pharmaceutical activities to save the mankind; especially in times of epidemic outbreak.
Cordycepin, the principal pharmaceutical molecule of Cordyceps militaris mushroom, is the only molecules on this Earth to neutralize SARS-CoV2 virus by targeting 1. Spike protein, 2. Main protease, 3. RNA dependent RNA polymerase, as well as 4. acting as Adenosine analog. If these data (research publications on its efficacy against SARS-CoV2) were available before the COVID outbreak, we could have saved a lot and lot using this lab-cultivated mushroom.
The tempt of growing a beautiful Cordyceps Colony on Agar Plate
Growing a Cordyceps militaris colony on agar plate is always tempting for any mycologist — the colony begins as a tight, white dot (inoculum), gradually expanding into a dense, cottony, and often beautifully brilliant orange, reflecting strain quality, media composition, and incubation mastery.
Culture media, mineral composition in the culture media, strains and incubation conditions affect the colony morphology of Cordyceps militaris- it is true for all other mushrooms, fungi, bacterial and other microbes. However, effect is LIGHT on colony morphology on agar plate is unique to Cordyceps militaris and few other microbes. Illumination induces development of carotenoid pigment resulting the brilliant orange color to the colony. The illumination pattern (day/night, continuous illumination, lux intensity, wavelength, etc.) also affects colony morphology besides carotenoid development.
Culture Media for Cordyceps militaris
The choice of a suitable agar culture media for Cordyceps militaris varies from lab to lab. The variable may include, but not limited to, acquaintance and perception of about any culture media, available, cost of media, formulation and evaluation of a new culture media at the particular lab, research publications at other labs and many more.
Potato Dextrose Agar (PDA) is the most commonly used fungal culture media. If going for PDA, avoid using raw potatoes as the change in quality of potatoes (season variation, type of potatoes, storage, sprouting in potatoes, etc.) may greatly affect the growth characteristics beyond our control. To get a reproducible result, use lab grade PDA media, through relatively costlier as their composition remains relatively constant among batches and manufacturers. The biggest drawback of PDA and PDA-based media is they lack any protein source. Protein is one of the four classes of biomolecules and crucial for optimum growth of all organisms including Cordyceps.
Yeast Malt extract Agar media (YMA) is also a good media for many mushrooms.
The list of these culture media may grow vast when summarized from different labs.
Vitamin supplementation is generally not required because Cordyceps militaris and most other mushrooms, like most other fungi, are capable of synthesizing vitamins of their needs.
A simple and effective may consists of a balanced nutrition from carbohydrate and proteins plus some minerals. The composition of such a media from our lab is summarized below-
Dextrose - 2.0%
Peptone - 1.2%
MgSo4.7H2O - 0.05%
Agar - 2.0%
This media works perfect for Cordyceps agar plate through we are always in search of something better.
Incubation Conditions for Cordyceps militaris Agar Plate
Incubate the inoculated Cordyceps militaris gar plate at 25 degree Celsius. Since the incubation period is going to be 2-3 weeks long, prefer sealing the petri dish with parafilm after inoculation to prevent its desiccation during incubation period.
In terms of growth pattern of Cordyceps militaris on agar plate, light triggers two (as I perceive at our lab) distinct phenomenon-
Carotenoid Development: The first and most obvious visible sign is carotenoid development by Cordyceps militaris mycelia. The mycelia first becomes cream-color within 2-3 hour of illumination, and gradually turn bright orange in 1-2 days.
Differential Growth Pattern under LIGHT: The growth pattern of Cordyceps militaris colony on agar plate under dark is different from that from illuminated. Under dark conditions, the mycelia growth is DENSE and CLOSELY PACKED. When illuminated, the mycelial growth is SPARSE (LOOSELY PACKED). Assuming (we assume) the mycelia growth rate (weight of new mycelia growing per unit time) remains the same under DARK and LIGHT on the agar media, the growth rate under LIGHT appears to be higher than DARK because the LOOSELY PACKED mycelia growing under light occupies greater surface area.
This difference in mycelia density is clearly visible on the agar plate.
Alternating DARK and LIGHT conditions: Most labs illuminate the agar plate in DAY/NIGHT or LIGHT/DARK fashion. Be it a 10 Hr Light /14 Hr Dark or 12Hr Light / 12 Hr Dark cycle or something else, some mycelia grows under light and some grow under dark within the same 24 hour frame. In other words, there is a ring of densely-packed mycelia ring (grew under dark) followed by a loosely-packed mycelia ring (grew under light). So, depending on the illumination pattern, the agar plate may show some concentric mycelia rings.
Zonation of Agar Plate: The intentional, unintentional or random illumination pattern of agar plate results concentric rings of densely-packed (grew under dark) and loosely-packed mycelia (grew under light) rings. The thickness of the mycelia rings is proportional to duration of incubation under light or dark, respectively. In all cases, the outermost ring is always the zone of active growth - it's density will depend on whether it developed under light or dark .
Optimizing Illumination for Cordyceps militaris agar plate:
An ideal Cordyceps militaris agar plate with dense mycelia growth and brilliant/vibrant orange color with least zonation is the visibly most appealing.
To obtain such a culture plate of Cordyceps militaris, the inoculated agar plate must in sealed with parafilm and incubated under DARK for 15 days. Allow continuous illumination of 24-48 hours after incubation in dark is over. A beautiful Cordyceps militaris agar plate will be ready !
Your suggestions and experiences are warmly welcomed !!!