A virus that infected the first animals hundreds of millions of years ago has become essential for the development of the embryo

Peer-Reviewed Publication

CENTRO NACIONAL DE INVESTIGACIONES ONCOLÓGICAS (CNIO)

 

IMAGE: 

NABIL DJOUDER, HEAD OF THE GROWTH FACTORS, NUTRIENTS AND CANCER GROUP AT CNIO

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CREDIT: ANTONIO TABERNERO / CNIO

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• At least 8% of the human genome is genetic material from viruses. It was considered ‘junk DNA’ until recently, but its role in human development is now known to be essential
• Researchers at the Spanish National Cancer Research Centre (CNIO) describe for the first time the role of these viruses in a key process in development, when cells become pluripotent few hours after fertilization
• The finding, published in Science Advances, is relevant for regenerative medicine and for the creation of artificial embryos

All animals have evolved thanks to the fact that certain viruses infected primitive organisms hundreds of millions of years ago. Viral genetic material was integrated into the genome of the first multi-cellular beings and is still in our DNA today. Researchers from the CNIO (Spanish National Cancer Research Centre) describe now in the journal Science Advances for the first time the role played by these viruses in a process that is absolutely vital for our development, and which occurs a few hours after fertilisation: the transition to pluripotency, when the oocyte goes from having two to four cells.

Before this step, each of the two cells of the embryo is totipotent, i.e. it may develop inside an independent organism; the four cells of the next stage are not totipotent but are pluripotent, because they can differentiate into cells of any specialised tissue of the body.

For Sergio de la Rosa and Nabil Djouder, first author and senior author respectively, the finding is relevant for the field of regenerative medicine and for the creation of artificial embryos, as it opens up a new way to generate stable cell lines in the totipotency phases. Djouder leads the  Growth Factors, Nutrients and Cancer Group at the CNIO.

We are 8% retrovirus

Genetic material from the now so-called 'endogenous retroviruses' was integrated into the genomes of organisms that may have been drivers of the Cambrian explosion, a period more than 500 million years ago when the world's seas underwent a biodiversity boom. Over the past decade, genetic sequences from these viruses have been found to make up at least 8-10% of the human genome.

“Until recently, these viral remnants were considered to be 'junk DNA', genetic material that was unusable or even harmful," explains De la Rosa. "Intuitively, it was thought that having viruses in the genome could not be good. However, in recent years we are starting to realise that these retroviruses, which have co-evolved with us over millions of years, have important functions, such as regulating other genes. It's an extremely active field of research”.

The transition from totipotency to pluripotency, a question of pace

The research published in Science Advances shows that the MERVL endogenous retrovirus sets the pace in embryo development, especially during the specific step of the transition from totipotency to pluripotency, and explains the mechanism that makes this happen.

"It is a totally new role for endogenous retroviruses," says Djouder. "We discovered a new mechanism that explains how an endogenous retrovirus directly controls pluripotency factors".

This new action mechanism involves URI, a gene that Djouder's group is researching in depth. Years ago, it was discovered that if URI is deleted in laboratory animals, embryos do not even get to develop. De la Rosa wanted to find out why, and which is how its link to the MERVL retrovirus was discovered.

A smooth transition

The findings show that one of the functions of URI is to enable the action of molecules essential for acquiring pluripotency; if URI does not act, neither do the pluripotency factors, and the cell remains in a state of totipotency. It turns out to be an endogenous retrovirus protein, MERVL-gag, which modulates the action of URI.

The researchers found that during the totipotency phase, when there are only two cells in the oocyte, expression of the MERVL-gag viral protein is high; this protein binds to URI and prevents it from acting. However, the levels gradually change, so that the levels of MERVL-gag viral protein go down and URI can enter into action: pluripotency appears.

As De la Rosa explains, "It's a smooth transition. When there is a high expression of viral protein, there are fewer pluripotency factors; as ERV expression decreases, URI stabilises such factors”.

Symbiotic co-evolution

“Our findings reveal symbiotic co-evolution of endogenous retroviruses with their host cells in order to guarantee the smooth and timely progression of early embryonic development," explain the authors in Science Advances.

In other words, the three-way relationship between the viral protein, URI and pluripotency factors is finely modulated, "to allow sufficient time for the embryo to adjust and coordinate the smooth transition from totipotency to pluripotency and cell lineage specification during embryonic development," concludes Djouder.

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JOURNAL

Science Advances

DOI

10.1126/sciadv.adk9394 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Endogenous retroviruses shape pluripotency specification in mouse embryos

ARTICLE PUBLICATION DATE

24-Jan-2024

 

One in five Colorado bumblebees are endangered, new report says

Reports and Proceedings

UNIVERSITY OF COLORADO AT BOULDER

 

IMAGE: 

THE HIGH COUNTRY BUMBLE BEE IS A UNCOMMON, HIGH-ELEVATION SPECIES NATIVE TO COLORADO.

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CREDIT: ADRIAN CARPER/CU BOULDER

On a cliffside at Mesa Verde National Park in southern Colorado, a fuzzy bee was industriously gnawing at the red sandstone. Making a loud grinding sound, the insect used its powerful jaws to drill tunnels and holes in rocks, where it would build a nest for raising offspring. 

The bee, known as Anthophora pueblo, is a type of digger bee native to Colorado. Discovered less than a decade ago, the bee has quickly become Adrian Carper’s favorite pollinator. 

“This is just one example of how crazily diverse our native bees are,” said Carper, an entomologist in the Department of Ecology and Evolutionary Biology at the University of Colorado Boulder and the CU Museum of Natural History. 

But those pollinators are in peril as a result of human activities, according to the first comprehensive report on Colorado’s native pollinating insects published by Carper and his collaborators earlier this month. 

The report summarized research on native pollinators in Colorado and found that in the last 35 years, populations of some pollinator species in the state have dropped by more than half. About 20% of Colorado’s 24 native bumblebee species are currently seeking federal protection by the Endangered Species Act due to a significant decline in their populations. 

“That’s a huge alarm call, and that’s only for species we have good data for,” Carper said, adding that this is likely an underestimate of the danger Colorado’s native pollinating insects are facing. 

In addition to bees and butterflies, other insects like beetles, flies and even mosquitoes also pollinate—many of them remain understudied. The report highlighted data from the Rocky Mountain Biological Laboratory, where even in a well-protected high-elevation meadow, the number of insects living there has dropped by 61% over the last 35 years.

Native pollinators are critical to Colorado’s ecosystem, agriculture and tourism industry.  

For example, the world-famous Rocky Ford cantaloupes, native to the small town in southeastern Colorado, are best pollinated by the state’s native squash bees. These bees have evolved special hairs to carry the cantaloupe’s particularly large pollen grains. In contrast, honeybees lack these special hairs and are inefficient at pollinating cantaloupe flowers.

“Our native bees have co-evolved with our native plants. We recreate in our beautiful high alpine mountains, because they are covered in colorful wildflowers, which wouldn’t be there if they didn't have our native pollinators to help them reproduce. Additionally, those native plants are integral to our rangelands, supporting over $5 billion worth of livestock across the state,” Carper said. 

According to the report, habitat loss, pesticides, climate change and non-native species including honeybees, are the main threats to native pollinators’ survival. 

Insects are cold-blooded animals that rely on the environment to regulate their body temperature. Many pollinators might not tolerate higher temperatures, and extreme weather events like droughts and floods could wipe out insect habitats. Climate change also affects when and how many plants are flowering, influencing the availability of nectar and pollen, which are the key sources of food for pollinators. 

Despite being an important agricultural pollinator, the western honeybee is a non-native species to Colorado. But with a growing interest in beekeeping, Colorado has seen a surge in the numbers of urban honeybee hives in recent years. Research has shown that these honeybees could compete with native bees for food, and potentially spread diseases and parasites. 
 
“We need to better educate beekeepers on subjects like disease management and swarm control to mitigate honeybees’ impacts on native pollinators,” Carper said.

The report highlighted priorities for the state to conserve native pollinators, including creating and connecting patches of habitat to allow pollinators to move between areas, and reducing pesticide use. 

For individuals, there is also room for action, Carper said. 

“Planting with native plants in our own backyards can certainly support our native pollinators.”

 

Humpback whales move daytime singing offshore, research reveals

Peer-Reviewed Publication

UNIVERSITY OF HAWAII AT MANOA

 

IMAGE: 

ANKE KÜGLER, MARC LAMMERS, ISABELLA CANEPA (STUDENT) AT THE OLOWALU LAND STATION CONDUCTING VISUAL SURVEYS. 

 

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CREDIT: ADAM PACK

Humpback whale singing dominates the marine soundscape during winter months off Maui. However, despite decades of research, many questions regarding humpback whale behavior and song remain unanswered. New research revealed a daily pattern wherein whales move their singing away from shore throughout the day and return to the nearshore in the evening. The findings were led by the University of Hawaiʻi, in partnership with NOAA’s Hawaiian Islands Humpback Whale National Marine Sanctuary, and published in Royal Society Open Science. 

“Singers may be attempting to reduce the chances of their song being drowned out among the cacophony nearshore when whale numbers are high,” said Anke Kügler, lead author of the study who was a doctoral student in the Marine Biology Graduate Program at UH Mānoa at the time of the research. “Further, we documented humpback whales moving closer to shore around sunset, possibly to avoid the offshore evening chorus of other animals.”

By using a combination of underwater listening devices and visual surveys, the research team was able to track both the physical movements and the acoustic patterns of whales in the high-density breeding grounds found in Hawai‘i. 

“This dynamic onshore-offshore movement of singers may be aimed at increasing the efficiency of the whales’ acoustic display, ensuring that other whales hear their songs,” said Marc Lammers, study co-author and research ecologist with NOAA’s Hawaiian Islands Humpback Whale National Marine Sanctuary.

“This is the first effort of its kind, to our knowledge, in which we used specialized acoustic sensors to localize individual singers relatively close to shore to understand daily variations in the distance to shore of these nearshore singers, their spacing, and their movement behavior,” said Kügler. “This helped contextualize the visual results and overcome some of the limitations from the land-based visual observations of movement.”

Humpback whale song is presumed to play an important role for breeding. The new findings highlight the significance for male singers of an environment that is teeming with acoustic commotion. Through their approach, the team identified potential drivers for the daily onshore-offshore migrations—nearshore environments that are too crowded with whales during the day and offshore areas that are too noisy with the chorus of other animals in the evening.  

“Discussions of noise pollution related to marine mammals have been dominated by concerns over anthropogenic noise,” said Kügler. “Potential acoustic masking from natural sources, including one whale masking another whale’s song, has been mostly overlooked. By exploring possible drivers of the observed patterns, we add to our understanding of how animals that rely on acoustic signals adopt behavioral strategies to mitigate masking from loud environments.”

Humpback whales are ecologically, economically, and culturally significant in Hawai‘i and their singing is iconic around the world.

“It is our collective kuleana (responsibility) to be the koholā’s (humpback whales) stewards,” said Lammers. “This and future work contributes to fulfilling the Sanctuary’s management plan by developing and implementing crucial research on humpback whales and their habitats to help maintain a healthy, sustainable population.”

In addition to Kügler and Lammers, co-authors on the study include Adam Pack, professor of psychology and biology at UH Hilo, founder and director of the UH Hilo Marine Mammal Lab and co-founder of the LOHE bioacoustics lab; and Aaron Thode and Ludovic Tenorio-Hallé at Scripps Institute of Oceanography, University of California.

Singing whake (IMAGE)

UNIVERSITY OF HAWAII AT MANOA

Singing whale. Hawaiian Islands Humpback Whale National Marine Sanctuary (NOAA permit 782-1719)

CREDIT

Hawaiian Islands Humpback Whale National Marine Sanctuary

Humpback whale chorus off Maui, Hawai'i (AUDIO)

UNIVERSITY OF HAWAII AT MANOA

Short recording of the humpback whale chorus off Maui with numerous males singing 

 

CREDIT

Oceanwide Science Institute

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JOURNAL

Royal Society Open Science

DOI

10.1098/rsos.230279 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Diel spatio-temporal patterns of humpback whale singing on a high-density breeding ground

ARTICLE PUBLICATION DATE

24-Jan-2024

 

Sparrows uniquely adapted to Bay Area marshes are losing their uniqueness

Increased interbreeding due to tidal marsh habitat loss caused saltwater Savannah sparrows to lose their genetic distinctiveness

Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - BERKELEY

 

IMAGE: 

PHRED BENHAM, A UC BERKELEY POSTDOCTORAL FELLOW WHO WROTE HIS PH.D. THESIS ON GENETIC VARIATION WITHIN SALTWATER-ADAPTED SAVANNAH SPARROWS, HOLDS ONE OF HIS SUBJECTS. THE SUBSPECIES HAS LOST 90% OF ITS TIDAL MARSH HABITAT OVER THE PAST 200 YEARS, MAKING THE BIRDS SUBJECT TO OUTBREEDING SUPRESSION BECAUSE OF INTERBREEDING WITH MORE ABUNDANT FRESHWATER-ADAPTED SAVANNAH SPARROWS.

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CREDIT: PHRED BENHAM, UC BERKELEY

The temperate climate of the San Francisco Bay Area has always attracted immigrants — animals and humans — that have had unpredictable impacts on those already living in the area.

For the bay's Savannah sparrow, a subspecies that lives in salty tidal marshes, increased immigration of its inland cousins over the past century has definitely been bad news.

A new genomic analysis of Savannah sparrows (Passerculus sandwichensis) from around the state — many of them collected as far back as 1889, their pelts stored in the Museum of Vertebrate Zoology at the University of California, Berkeley — shows that over the past 128 years, the Bay Area's sparrow's adaptation to salt water is being diminished by interbreeding with inland sparrows adapted to fresh water.

The result is stable levels of genetic diversity among coastal Savannah sparrows in Northern and Central California, but a loss of the genetic variants that make them adapted to tidal marshes. This could affect the bird's ability to survive in tidal marshes, where it subsists on saltwater and salty crustaceans, something freshwater birds are ill-adapted to.

The surprise finding, published last week in the journal Global Change Biology, can be explained in part by the steep state-wide decline in tidal marshes, which are wetlands subject to the tidal influx of salty ocean water. The Bay Area has seen a 90% decline in tidal marshland since the 1800s, which has reduced Savannah sparrow populations to the level that interbreeding with immigrants is affecting their unique saltwater adaptation.

"There seem to be increasing levels of gene flow from eastern California into places like the Bay Area, potentially due to the local population becoming a sink where the local breeders can't really produce enough offspring to maintain a population," said Phred Benham, a postdoctoral fellow at UC Berkeley and leader of the study. "So you get the influx of immigrants from another population. The migrants think it's a nice place to stay and try to set up a nest, and there's this opportunity for gene flow to occur into the residents."

That gene flow from sparrows adapted to fresh water into saltwater-adapted sparrows means that the gene variants, or alleles, that allow tidal marsh sparrows to exist in a high-salt environment — by producing larger kidneys, for example — are being lost.

"The inland areas where grasslands remain extensive are producing large numbers of these birds, and they have to go somewhere. And so the Bay Area is a destination," said Rauri Bowie, UC Berkeley professor of integrative biology and curator of birds in the Museum of Vertebrate Zoology (MVZ). "They're coming in, but they are not adapted to breed in that environment. So they don't do well, and they're introducing maladaptive alleles — freshwater-adapted alleles into saltwater-adapted populations. And some of these coastal populations are endangered. If you go to these habitats, you see lots of Savannah sparrows, but there's something going on underneath the hood that's a lot more complex in these kinds of specialized environments."

A subspecies of special concern

With 17 recognized subspecies throughout North America, Savannah sparrows are commonplace, Bowie said. But the rare subspecies adapted to live in saltwater marshlands are considered threatened. Two occur in California, a northern subspecies (P. s. alaudinus), which is listed by the state as a "species of special concern," and a federally protected southern subspecies called the Belding's Savannah sparrow (P. s. beldingi), which occurs around San Diego and Tijuana, Mexico.

The good news for the northern marshland subspecies, Benham noted, is that tidal wetlands around the San Francisco Bay estuary are protected and growing, potentially allowing coastal Savannah sparrow populations to increase.

"There's a huge amount of tidal restoration efforts underway in the Bay Area, and Savannah sparrows aren't the only ones that depend on this. One of the most critically endangered species in the Bay Area is the salt marsh harvest mouse. There's a lot of federal money going into protecting their habitat, which I think ultimately would benefit the Savannah sparrows," he said. "I think it would be really great to revisit these populations in 10 years to see if this trend is ongoing or if tidal marsh restoration has allowed the locals to reestablish their populations and their dominance."

Continued monitoring of immigrant sparrows, Bowie said, "would give a sense of whether this genetic swamping is continuing and how quickly it's happening. I'd hope that as marshes are restored, that would be mitigated. But we don't know that."

Benham and Bowie, assisted by Jennifer Walsh of the Cornell Laboratory of Ornithology at Cornell University in Ithaca, New York, set out to ask an important evolutionary question: How does habitat loss affect the genetic diversity of animals that occupy that habitat?

"We wanted to test a very simple prediction, that there is reduced genetic diversity associated with habitat loss," Benham said.

For the genetic analysis, Benham obtained DNA samples from Savannah sparrows captured around the state between 1889 and 2017. To get DNA from museum samples, he scraped skin cells from the birds' toe pads. For comparison, he collected blood or tissue samples from living birds he had encountered over the last decade studying Savannah sparrow populations around the Bay Area for his Ph.D. thesis from the University of Montana.

Using a technique called exome capture, he profiled the DNA from 219 individuals and looked for genetic variation in areas of DNA that had previously been identified as important to the saltwater adaptation of marshland sparrows. Some of these adaptations he had discovered himself in studying these Savannah sparrows. For example, not only are their kidneys larger and thus able to remove more salt from the birds' urea, but their skin is less permeable to water. To make up for a reduced reliance on evaporative cooling, like sweating, to shed heat, their bills have gotten larger, which allows more heat to be lost from the blood flowing through. All these adaptations make up for the fact that songbirds never evolved a solution common to other seaside birds — the ability to excrete excess salt through nasal glands.

The researchers found that the genetic diversity of the Southern California subspecies, the Belding's Savannah sparrow, had declined slightly, but that it had been low even in the 1880s.

Genetic diversity in the Northern California subspecies, however, remained relatively high over the past century, likely due to immigration from inland sites. But this immigration led to gene alleles in regions of the genome involved in saltwater adaptation that were more like the alleles found in freshwater-adapted sparrows.

Bowie noted that the results bear on a major debate in conservation biology today — whether it is wise to bolster small, threatened, inbred populations by breeding them with related populations. In the case of the Savannah sparrow, such outbreeding reduced adaptation to the environment.

"Here, we're showing that if gene flow is happening across these steep environmental gradients, it may have significant negative effects on the local population," Benham said.

"It's actually quite a hard thing to demonstrate the effects of outbreeding," Bowie emphasized. "Having access to the historical series of the museum specimens from before saltmarshes were transformed in the bay to compare with modern birds helps you make the case that outbreeding depression is having a significant effect on the populations. The genetic diversity looks great, but it's masking an outbreeding depression effect."

Benham's work was supported by a Postdoctoral Research Fellowship in Biology from the National Science Foundation (1812282).

The San Francisco Bay Area's tidal marshes, such as this restored marsh in Hayward, California, are home to many animals adapted to saltwater environments, including a local subspecies of Savannah sparrow and the salt marsh harvest mouse. These adaptations, caused by specific gene variants, can be compromised by outbreeding with migrant populations that do not have these varients.

CREDIT

Phred Benham, UC Berkeley

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JOURNAL

Global Change Biology

DOI

10.1111/gcb.17126 

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Spatial variation in population genomic responses to over a century of anthropogenic change within a tidal marsh songbird

 

Microplastics may be accumulating rapidly in endangered Galápagos penguins’ food web

Peer-Reviewed Publication

UNIVERSITY OF BRITISH COLUMBIA

 

IMAGE: 

A GALÁPAGOS PENGUIN IS PERCHED ON THE MOLTEN ROCK OF THE ISABELA ISLANDS. THE AUTHORS CAPTURED THIS PHOTO DURING A 2021 EXPEDITION TO COLLECT MICROPLASTICS IN THE GALÁPAGOS MARINE RESERVE.

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CREDIT: IMAGE CREDIT: KARLY MCMULLEN, CC-BY 4.0 (HTTPS://CREATIVECOMMONS.ORG/LICENSES/BY/4.0/)

Microplastics, with a size from 1 micron to < 5 millimeters, are pervasive pollutants that have been found in all parts of the global ocean, and have made their way into the marine food webs. Researchers, led by University of British Columbia UBC’s Institute for the Oceans and Fisheries scientists and Ecuadorian researchers from Galápagos and the ESPOL Polytechnic School (Guayaquil, Ecuador), looked closely at how microplastic bioaccumulation was affecting the endangered Galápagos penguin (Spheniscus mendiculus) as an indicator species to trace how deeply microplastic bioaccumulation has entered the food web in the isolated Galápagos Islands.

An analysis of seawater collected around Santa Cruz Island, a human-populated island, with nearby Galápagos penguin colonies revealed plastic particles. Using models that focused on the Galápagos penguin diet (barracuda, sardine, herring, salema, and anchovy), and on penguin scat, researchers intuited a unique Galapagos penguin food web model using Ecopath and Ecosim (EwE) ecosystem modeling with the Ecotracer approach to track the bioaccumulation potential of microplastics in the penguins’ foodweb. They also applied a wider model for Bolivar Channel Ecosystem (between Fernandina and Isabela islands) and part of the penguin’s habitats, located at the western regions of the Galápagos Islands.

The model predictions showed a rapid increase in microplastic accumulation and contamination across the penguins’ prey organisms resulting in Galápagos penguin showing the highest level of microplastics per biomass, followed by barracuda, anchovy, sardine, herring, and salema and predatory zooplankton.

“The model predictions highlight the accumulation behavior and residence time of microplastics in the gut,” said Karly McMullen, first author and a former MSc student at the Institute for the Oceans and Fisheries at the University of British Columbia. “With microplastics emerging as a prominent ocean pollutant, entering the environment every day, there is a growing concern for marine fauna and coastal wildlife, particularly if this anthropogenic threat is reaching even the most remote and protected areas such as the Galápagos Archipelago.”

Senior autho, honorary research associate, and Principal Investigator of the Ocean Pollution Research Unit at Institute for the Oceans and Fisheries at the University of British Columbia, Dr. Juan Jose Alava, agreed. "The goal of this food web bioaccumulation modeling work was to provide science and data to support risk management of hazardous plastic waste, reduce microplastic emissions in the oceans and marine remote UNESCO Heritage sites such as the Galapagos Islands, and inform local and international marine policy to conserve endangered, endemic seabird species of Galapagos Marine Reserve."

“It is imperative that we prioritizing efforts to reduce the input of microplastics into vulnerable ecosystems and food webs, particularly such as that of the endangered Galapagos penguin.”

“Modelling microplastic bioaccumulation and biomagnification potential in the Galápagos penguin ecosystem using Ecopath and Ecosim (EwE) with Ecotracer”, was published in PLOS ONE.

 

A gang of Galápagos penguin (Spheniscus mendiculus) resting on lava rock and vigilant in front of the ocean observed in October 2021 at Isabela Island, Galapagos Islands (Ecuador). Note, the floating plastic buoy (made of either expanded polystyrene (known as Styrofoam), or polyurethane) at the background. 

CREDIT

Photo credit: Dr. Juan José Alava (Ocean Pollution Research Unit, IOF)

JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0296788 

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Modelling microplastic bioaccumulation and biomagnification potential in the Galápagos penguin ecosystem using Ecopath and Ecosim (EwE) with Ecotracer

 

Foodborne-pathogen Listeria may hide from sanitizers in biofilms

The finding could result in more effective sanitation procedures, leading to safer food supply, researchers said

Peer-Reviewed Publication

PENN STATE

 

IMAGE: 

THE RESEARCHERS TESTED THE BIOFILM-FORMING ABILITY OF ASSEMBLAGES COMPRISING THE FOODBORNE PATHOGENS LISTERIA MONOCYTOGENES AND ENVIRONMENTAL MICROBIOTA.   

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CREDIT: PENN STATE

UNIVERSITY PARK, Pa. — An estimated 1,600 people in the U.S. contract a serious infection from Listeria bacteria in food each year and, of those individuals, about 260 people die, according to the Centers for Disease Control and Prevention. Penn State researchers may now better understand how the bacteria, called Listeria monocytogenes, survive and persist in fruit-packing plants by evading and surviving sanitizers.  

According to their study, which is now available online and will be published in the June issue of the journal Biofilm, biofilms — comprising otherwise harmless microorganisms that attach to each other and the food surface — result in a kind of shield that surrounds and protects the Listeria. The findings may result in changes to sanitation protocols in food-processing facilities that promise to diminish contamination of food with Listeria, the researchers said.

“We found two groups of microorganisms in the tree fruit packing environments, Pseudomonadaceae and Xanthomonadaceae, that are very good at forming biofilms and protecting Listeria monocytogenes,” said corresponding author Jasna Kovac, the Lester Earl and Veronica Casida Career Development Professor of Food Safety. “Biofilms represent a physical barrier that reduces the effective diffusion and antimicrobial action of sanitizers and is hypothesized to increase L. monocytogenes’ tolerance to sanitizers used in food processing facilities.”

As a result of the biofilms shielding the pathogen, the sanitizers are not as effective in killing Listeria monocytogenes, explained Laura Rolon, who recently earned her doctorate from Penn State and spearheaded the study.

“Our research suggests that if packing facilities are having a recurring problem with Listeria monocytogenes, they may need to assess whether biofilm-forming microorganisms are causing it,” she said.

This study’s results indicate a need to assess the efficacy of commonly used sanitizers against non-pathogenic biofilm-forming microorganisms commonly found in the food processing environments to prevent biofilms from establishing, Kovac explained. The results of further assessments could help inform practical recommendations for the industry, such as application concentrations and times, to prevent biofilm formation and improve the control of Listeria monocytogenes in these environments.

In future workshops and short courses, Penn State Extension educators will communicate the research findings to professional organizations dedicated to sanitation in food-processing facilities, noted study co-author Luke LaBorde, professor of food science and extension specialist.

“The findings of this research project will inform and enhance sanitation protocols and extension training efforts targeted at the tree-fruit industry to effectively control L. monocytogenes,” said LaBorde, an expert in the tracking of Listeria monocytogenes in produce production and processing environments. The bridge between scientific discovery and dissemination among stakeholders, he added, is a vital part of this work and a prime example of the mission of a land-grant university like Penn State.

To that end, Penn State Extension routinely offers workshops and other resources to communicate research findings, such as the Listeria monocytogenes-biofilms study results, and promote other best practices for controlling foodborne pathogens. These trainings are typically attended by food-processing plant professionals, representatives of industry associations, food safety consultants and government inspectors.

Partially because of their research on Listeria monocytogenes and biofilms, Kovac and LaBorde won the Integrated Team Award from the College of Agricultural Sciences late last year.

Other co-authors include M. Laura Rolan, Olena Voloshchuk and Katelyn V. Bartlett, all with the Department of Food Science in the College of Agricultural Sciences at Penn State. 

The U.S. Department of Agriculture supported this research. 

Microbiota isolated from fruit packing environments growing in lab dishes. 

CREDIT

Penn State

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JOURNAL

Biofilm

DOI

10.1016/j.bioflm.2024.100177 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

Multi-species biofilms of environmental microbiota isolated from fruit packing facilities promoted tolerance of Listeria monocytogenes to benzalkonium chloride

ARTICLE PUBLICATION DATE

24-Jan-2024