100 for 100: Microbes, Mutations, Moonshots and More

Item 76/100: Could Chernobyl Fungus Shield Space Explorers?
Leka Papazisi, PhD, Principal Scientist, Product Lifecycle Management, ATCC Research & Industrial Solutions
ATCC® 11289™ – Cladosporium sphaerospermum Penzig

Cosmic radiation is one of the biggest obstacles facing astronauts on long-term missions. Surprisingly, a fungus found thriving in the ruins of Chernobyl—Cladosporium sphaerospermum—may offer a solution. This resilient microbe uses melanin, the same pigment in human skin, to convert radiation into energy through a process called radiosynthesis, much like plants harness sunlight. To test its protective potential, scientists grew a thin layer of the fungus aboard the International Space Station. In just 26 days, it reduced radiation by almost 2%.¹ Further analysis suggests that an 8-inch-thick layer could lower Mars’s surface radiation to levels safe for humans, potentially reducing exposure from 400 mSv—roughly 66 times Earth’s average—to much safer doses.² What sets C. sphaerospermum apart is its self-replicating nature and minimal resource needs.

Astronauts could grow their own living shields on the Moon or Mars, sidestepping the costly need to transport heavy shielding from Earth. While further research is needed to integrate fungal shielding with other materials, the microbe’s hardiness in extreme environments makes it a promising candidate for future space habitats. Harnessing a survivor from one of Earth’s most radioactive environments, we may find a natural, sustainable defense against cosmic radiation—a testament to evolution’s ingenuity and the surprising allies we can find in nature’s most unlikely places.

Item 77/100: Measles, from Outbreak Isolate to Vaccine
Eric Mazur, MS, Senior Biologist
ATCC® VR-24™ – Measles virus

Measles virus is a highly infectious human pathogen. Each case may result in the infection of 12-18 new individuals in a naive population.³ Prior to vaccination efforts in the United States, the virus caused regular outbreaks and an average of 500 reported measles deaths annually.^4,5 In 1954, Peebles and Enders isolated the measles virus in cell culture for the first time with clinical isolates collected during an outbreak at a Massachusetts boarding school. The virus derived from these isolates—named the Edmonston B strain—was attenuated to develop and license the first measles vaccine in 1963.^6,7 This live attenuated virus had lower pathogenicity than circulating measles viruses and protected patients against severe disease from infection. It was distributed until 1975 when it was replaced by the Edmonston-Enders vaccine strain, which is still included in the measles, mumps, rubella (MMR) vaccine today.⁵ Measles vaccination programs have resulted in over a 95% decrease in incidence of the virus, but the virus continues to cause outbreaks in unvaccinated populations.⁵ Enders deposited the Edmonston strain to ATCC in 1958, which was given the catalog number VR-24™. ATCC continues to provide access to the Edmonston strain to researchers worldwide.

Item 78/100: Balamuthia: The Brain-Eating Amoeba
Baisali Ray, PhD, Senior Technical Writer
ATCC® 50209™ – Balamuthia mandrillaris Visvesvara et al.

In 1986, a pregnant mandrill—the largest species of monkey—at the San Diego Zoo suddenly became lethargic and died. Postmortem examination of the brain tissue revealed a previously unidentified brain-eating amoeba, later named Balamuthia mandrillaris in honor of the late UC Berkeley zoologist William Balamuth. This isolate was deposited to ATCC that same year. B. mandrillaris is an amphizoic protozoan capable of living freely in soil or as a parasite in a host. It remains the only known species in its genus.

Balamuthia causes granulomatous amoebic encephalitis (GAE), a rare and often fatal central nervous system infection. With fewer than 200 cases reported worldwide so far, and a survival rate of less than 5%, GAE is among the most lethal infectious diseases known.⁸

The organism has two distinct life stages: an active, infectious trophozoite and a dormant cyst. The cysts are highly resilient due to their protective cell walls, allowing them to survive harsh environments, resist drugs, and contribute to recurrent infections. Both forms can enter the human body, through wounds in the skin or via inhalation through the nose.

Common routes of exposure include contact with contaminated soil—such as during gardening or recreational activities (do not forget wearing protective clothing when working with soil)—as well as organ transplantation from infected donors. Once inside the host, Balamuthia can invade the brain and skin, causing GAE and cutaneous balamuthiasis.⁹ It crosses the blood-brain barrier and starts killing host cells through phagocytosis and induces apoptosis. Clinical progression typically begins with nonspecific symptoms such as headache, nausea, and low-grade fever, advancing to seizures, coma, and ultimately death.¹⁰

The high mortality rate is caused by difficulty in diagnosis, often misdiagnosis, and the lack of effective, targeted therapies. For timely diagnosis, a high degree of clinical suspicion and familiarity of the pathologist with the amoeba in tissue samples are needed. Current FDA-approved treatments are limited by poor blood-brain barrier penetration and significant side effects.¹¹ There is an urgent need for improved diagnostic tools, targeted therapeutics—such as nanoparticle-conjugated drugs—and in vitro drug efficacy studies, where ATCC resources could play a key role.

Item 79/100: ATCC Products in Space
Shazia Hamid, MBBS, Technical Manager
ATCC® MSA-2003™ – 10 Strain Even Mix Whole Cell Material

ATCC Federal Solutions, in collaboration with Dr. Scott Tighe at the University of Vermont (UVM), successfully customized the 10 Strain Even Mix Whole Cell Material (ATCC® MSA-2003™), an environmental microbiome standard, into specialized vials for use aboard the International Space Station (ISS). The BEI Bacteriology team, led by Chinchu Johny, Shazia Hamid, and Dr. Marco Riojas, produced 50 vials of MSA-2003-ISS, each containing a lyophilized whole-cell mix of 10 distinct bacterial species adapted to specialized Sarstedt tubes. These vials were shipped to UVM on January 16, 2023, and subsequently launched to the ISS via SpaceX29 for use in microgravity experiments.

According to NASA, the ISS National Lab, orbiting 248 miles above Earth, serves as a fully functional research facility. It enables the transformation of traditional ground-based experiments into flight-ready payloads. Onboard studies of spaceflight effects on living organisms help advance pharmaceutical development and enhance Earth-based research in biology, medicine, agriculture, and biotechnology.

“This is the first time that some of our products will be used in space to study human health in microgravity. Our participation in this type of pioneering research is just one more example of how we continue to raise the bar in the development and application of biomaterials, bio information, and standards used in biological research,” said ATCC chairman of Board, Raymond H. Cypess, DVM, PhD.

Item 80/100: A Parasite that can Alter Behavior  
Susan Gottshall, BS, MBA, Technical Manager
ATCC® 50174™ – Toxoplasma gondii (Nicolle and Manceaux) Nicolle and Manceaux

Toxoplasma gondii is a protozoan parasite that infects a variety of host organisms causing a disease known as toxoplasmosis. T. gondii is one of the most common infectious parasites in the world and could lay dormant in up to 40% of the world's population. Additional host species are all warm-blooded animals including all livestock species, rodents, and birds. T. gondii has only ever been observed to reproduce in species from the family Felidae, which includes house cats and their wild relatives such as lions, cheetahs, and tigers. Up to 40% of domestic cats in the U.S. have antibodies against T. gondii, meaning they were infected with the parasite at some point in their lives.

The most common ways humans contract toxoplasmosis is by ingesting undercooked meat containing tissue cysts or by consuming food or water contaminated with oocysts from cat feces.  Most people infected with T. gondii have no symptoms. Pregnant women, infants and people with weakened immune systems can develop severe cases of toxoplasmosis that causes long-term damage. There are currently no vaccines or treatments to prevent or cure toxoplasmosis.¹²

What makes T. gondii particularly interesting are the recent studies that have earned T. gondii the nickname the "mind-control parasite." Studies in mice and rats have demonstrated that T. gondii infection reduces fear and anxiety responses and increases risk taking behavior in rodents. The prevalence of this parasite with its unique characteristics, limited therapeutic options, and potential for significant alterations in behavior make it a target for researchers worldwide.¹³ To understand its life cycle, long-term consequences on host species behavior, and contribute to Toxoplasma research, ATCC offers over 70 parasite strains—including type strains I (ATCC® 50174™), II (ATCC® 50611™), and III (ATCC® 50861™)—and genomic DNAs (ATCC® 50174D™).

Item 81/100: New type of Drug-Resistant Isogenic Cell Lines
Fang Tian, PhD, Director Cell Biology Content and Product Development
ATCC® CRL-1619IG-1™ – KRAS mutant-A375 Isogenic Cell Line

The development of next-generation anti-cancer drugs, biologics, and immunotherapies continues to face major challenges, most notably the low success rates of seemingly promising experimental therapies in human clinical trials. Compounding this issue is the persistent problem of drug resistance in cancer, which has significantly limited the desired clinical outcomes.¹⁴ Initial successes with early anti-cancer drugs may generate optimism, but such enthusiasm is often moderated by subsequent evidence of disease relapse.¹⁵

Traditionally, drug-resistant cell line models have been developed through long-term cell culture in the presence of the anti-cancer drug. However, this approach often results in genotypic and phenotypic instability and necessitates continuous exposure to the drug during culture. To overcome these limitations, ATCC used CRISPR/Cas9 gene-editing technology to create a novel type of drug-resistant cell model. This approach allows for precise genomic modifications in the parental cell lines.¹⁶

The BRAF V600E mutation occurs in approximately 60% of melanomas. Resistance to BRAF inhibitor drugs has been a long-standing challenge in the treatment of melanoma with the BRAF V600E mutation. Using CRISPR gene editing, ATCC created a panel of drug-resistant models¹⁷—CRL-1619IG-1™, CRL-1619IG-2™, CRL-1619IG-3™—within A375 melanoma cell line, which naturally contains BRAF V600E. These novel isogenic drug resistance lines recapitulate additional mutations such as KRAS G13D, NRAS Q61K and MEK1 Q56P that developed in resistant cancer patients.

Compared to the parental line, these engineered isogenic cell models demonstrate that targeted gene modifications at the endogenous level directly confer significant resistance to BRAF inhibitors. They recapitulated the resistance to BRAF inhibitors in vitro like the mutations found in patients with acquired resistance to BRAF inhibitors during treatment. They represent a new type of drug resistance model that contains a defined genetic resistance mechanism. Without being maintained in a drug selection culture environment, these cell lines hold the permanent drug resistance characteristics.

The new CRISPR/Cas9 engineered isogenic models of acquired BRAF inhibitor resistance in BRAF V600E melanoma represent a major step forward for both the study of acquired BRAF inhibitor resistance and for the screening and development of novel therapeutics and treatment regimens that can bypass or overcome existing resistance mechanisms.

Item 82/100: Human Microglial Cell Line
Hyeyoun Chang, PhD, Senior Scientist
ATCC® CRL-3304™ – HMC3 (Human Microglial Cell Line)

Microglial cells are the resident macrophages of the brain that represent the first line of immune defense within the central nervous system. These cells play essential roles in maintaining the neuronal environment, regulating brain development, and promoting tissue repair.¹⁸ Although indispensable in many research areas, human microglial cells are difficult to obtain. Not only is sourcing human brain tissue for research highly regulated and ethically complex, but the isolation of primary microglial cells in their resting state is also technically challenging.¹⁹ Immortalized microglial cell lines offer advantages such as simple maintenance, high reproducibility, and unlimited growth suitable for high throughput assays.

HMC3 (human microglia clone 3) is an immortalized human microglial cell line originally derived from human embryonic brain and immortalized with SV40 large T antigen in the mid-1990s.²⁰ These cells express microglia-associated markers, such as IBA1, and MHCII, CD68, and CD11b when activated by interferon-gamma.²¹ Originally named CHME-3, there was long-standing confusion about its origins.²² HMC3 cell line was recently authenticated by ATCC and is one of the most widely used and referenced human microglial cell lines today. 

Item 83/100: Yellow Fever Surveillance with MAC-HD ELISA Assay
Katie Alvey, Technical Manager
ATCC® YF-500™ – YF MAC-HD ELISA Kit

Yellow fever is a life-threatening viral disease transmitted by infected mosquitoes, capable of triggering large-scale outbreaks in unvaccinated populations. These outbreaks can lead to high rates of illness and death, along with severe social and economic disruption. Because its symptoms often mimic those of other serious illnesses—such as hepatitis and hemorrhagic fevers like Ebola—accurate and timely diagnosis is essential. There are two recommended primary methods for confirming yellow fever: nucleic acid testing (NAT) and serological detection of yellow fever-specific IgM antibodies. Among these, IgM serology remains the only viable option once the brief NAT detection window has passed. Reliable IgM testing is therefore critical for effective disease surveillance, outbreak detection, and risk assessment. It also plays a key role in guiding rapid response efforts, mass vaccination campaigns, and routine immunization strategies. However, timely detection remains a significant challenge in many low-resource settings. Traditional PCR-based methods are limited to early stages of infection, leaving a diagnostic gap as the disease progresses. To address this, ATCC manufactures a serum-based ELISA assay designed to detect yellow fever-specific IgM antibodies, whether from natural infection or post-vaccination response. This assay enhances surveillance capabilities by enabling accurate detection beyond the early symptomatic phase. Currently, the YF MAC-HD ELISA kit is distributed in over 24 countries, in support of the US government’s public health initiative to monitor, contain, and ultimately prevent yellow fever outbreaks. This same methodology can be applied to other vaccine-preventable diseases, strengthening global diagnostic infrastructure and improving preparedness for future outbreaks.

Did you know?

World Space Week is October 4-10 and ATCC products are no strangers to outer space. Our products have been to space to help study microgravity and we have three type strains that were isolated from the Mars Exploration Rover Spacecraft clean room from the Jet Propulsion Laboratory in California.

References

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3. Anderson RM, May RM. Directly transmitted infections diseases: control by vaccination. Science 215(4536): 1053–1060, 1982. PubMed: 7063839
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13. Baker H. 10 surprising facts about the “mind-control” parasite Toxoplasma gondii. LiveScience. Published February 1, 2023. Accessed September 2, 2025. https://www.livescience.com/surprising-toxoplasma-gondii-facts.
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17. Turner E, et al. CRISPR/Cas9 Edited RAS & MEK Mutant Cells Acquire BRAF and MEK Inhibitor Resistance with MEK1 Q56P Restoring Sensitivity to MEK/BRAF Inhibitor Combo and KRAS G13D Gaining Sensitivity to Immunotherapy. Cancers (Basel) 14(21): 5449, 2022. PubMed: 36358868
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