Tuesday, July 18, 2023

Bioluminescent bacteria coordinate signaling to colonize squid’s light organ

PENN STATE

Bioluminescent bacteria and the Hawaiian bobtail squid have formed a longstanding mutually beneficial relationship. How the bacteria coordinate their behavior to colonize the squid—through cellular signaling and cues from the environment—is detailed in new study led by Penn State researchers.

A paper describing the study is available online in the journal eLife. The researchers also show that the mechanism that they describe is likely to be widespread in a broad array of bacteria and that understanding this coordination of cellular signaling will be important for understanding how bacteria colonize their hosts more generally.

“The bacteria we study, known as Vibrio fischeri, is associated with many different marine hosts, but its association with the Hawaiian bobtail squid is the best characterized,” said Tim Miyashiro, associate professor of biochemistry and molecular biology in the Penn State Eberly College of Science and the leader of the research team.

The squid have a specialized light organ tucked within the underside of their mantle that is occupied by the bacteria. The bacteria’s glow is believed to help camouflage the squid when viewed by potential predators from below. The bacteria, in turn, get nutrients from the squid to support their growth. The squid, however, are not born with the bacteria in their light organs. Bacteria from the environment must make their way into the light organ after the squid hatch.

“Aspects of bacterial behavior in the light organ have been characterized,” said Miyashiro, “but the cellular mechanisms that allow the bacteria to colonize the squid in the first place are still poorly understood, so we set out to investigate how the bacteria initiates colonization.”

Inside the light organ, bacterial behavior is coordinated through “quorum sensing.” The bacteria release signaling molecules that increase in concentration as the bacterial population grows and becomes denser. When enough bacteria are present—when a quorum is reached—a signaling pathway is activated such that the bacteria will begin to produce bioluminescence and their ability to move is suppressed. Prior to colonizing the light organ, the bacteria form large aggregates of cells as well, but if the quorum sensing pathway were activated they might not be motile enough to move into the light organ.

“So, the question is ‘how do the bacteria avoid the quorum sensing pathway when they form these large aggregates outside of the squid and instead initiate behavior that promotes colonization?’” said Miyashiro. “What we saw was that the aggregation pathway activates the production of a small RNA molecule that is normally repressed by quorum sensing. Therefore, when the signaling pathway that leads to aggregation is activated outside the squid, the RNA molecule is expressed, which enables the cells to bypass quorum sensing to remain motile and dark.”

The small RNA--called Qrr1—is part of the quorum sensing pathway that represses the ability of the bacteria to produce bioluminescence and promotes motility until a quorum is reached. When a quorum is reached, expression of Qrr1 is subsequently shut down.

“Qrr1 has also been shown to be important for promoting colonization,” said Miyashiro. “You might expect that Qrr1 would be repressed during aggregation like it is during quorum sensing, but that is not what happens. So, we performed a number of experiments aimed at characterizing the molecular control of Qrr1 expression during aggregation.”

The researchers showed that Qrr1 can be activated by a transcription factor—a protein that controls when and where genes are turned on in a cell--that also controls genes involved in aggregation. The transcription factor—a protein called SypG—is similar to the one used to regulate Qrr1 by the quorum sensing pathway This similarity enables SypG to promote expression of Qrr1 in the aggregates during colonization and ensures Qrr1 is not expressed once inside the light organ to allow bioluminescence.

“This complex regulatory architecture that controls Qrr1 expression allows it to play these two important roles and helps coordinate the shift in behavior from colonization to bioluminescence,” said Miyashiro. “When we look across the bacterial family that includes V. fischeri, we see very similar structures that suggest to us that this type of coordination is likely to be important for many symbiotic bacteria.”

In addition to Miyashiro, the research team at Penn State includes Ericka D. Surrett, graduate student in the biochemistry, microbiology, and molecular biology (BMMB) program; Kirsten R. Guckes, postdoctoral scholar in Miyashiro’s lab; Shyan Cousins, and undergraduate student; Terry B. Ruskoski, BMMB graduate student; Andrew G. Cecere, research technologist in Miyashiro’s lab; and C. Denise Okafor, assistant professor of biochemistry and molecular biology and of chemistry. The research team also includes Denise A. Ludvik and Mark J. Mandel at the University of Wisconsin-Madison.

This work was supported by the U.S. National Institute of General Medical Sciences, the Howard Hughes Medical Institute Gilliam Fellowship, and National Institute of Allergy and Infectious Diseases Fellowship. Miyashiro is a member of the One Heath Microbiome Center at Penn State and the Penn State Huck Institutes for the Life Sciences.

JOURNAL

eLife

DOI

10.7554/eLife.78544.sa0

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Two enhancer binding proteins activate σ54-dependent transcription of a quorum regulatory RNA in a bacterial symbiont

Why are mosquitos so obsessed with me? (video)

Business Announcement

AMERICAN CHEMICAL SOCIETY

Why are mosquitos so obsessed with me? (video) — IMAGE: SOME PEOPLE ARE MORE ATTRACTIVE TO MOSQUITOS THAN OTHERS, AND NEW RESEARCH IS STARTING TO SHOW WHY. THIS REACTIONS EPISODE DIVES INTO THE CHEMISTRY OF THE MOLECULES ON OUR SKIN THAT MAKE SOME OF US SO MUCH MORE APPEALING TO THESE PESKY INSECTS. IT ALSO REVEALS WHICH PRODUCTS WE CAN USE TO TRY TO DETER THEM. HTTPS://YOUTU.BE/VYUUG72GWB0 view more
CREDIT: THE AMERICAN CHEMICAL SOCIETY

WASHINGTON, July 17, 2023 — Some people are more attractive to mosquitos than others, and new research is starting to show why. This Reactions episode dives into the chemistry of the molecules on our skin that make some of us so much more appealing to these pesky insects. It also reveals which products we can use to try to deter them. https://youtu.be/VYUug72GWB0

Reactions is a video series produced by the American Chemical Society and PBS Digital Studios. Subscribe to Reactions at http://bit.ly/ACSReactions and follow us on Twitter @ACSReactions.

The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.

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STILL NO REASON TO DROP THEM ON THEIR HEADS

Children’s IQs not diminished by concussion

UCalgary led study published in Pediatrics can reduce parental fears

Peer-Reviewed Publication

UNIVERSITY OF CALGARY

Keith Yeates — IMAGE: PRINCIPAL INVESTIGATOR KEITH YEATES SAYS THE STUDY MAY BRING SOME RELIEF TO PARENTS CONCERNED ABOUT THEIR CHILD'S RECOVERY FROM CONCUSSION. view more
CREDIT: RILEY BRANDT, UNIVERSITY OF CALGARY

The angst parents feel when their children sustain injuries is surely one of the universal conditions of parenthood. That anxiety is heightened greatly when those injuries involve concussions. But a new study led out of the University of Calgary, published today in the medical journal Pediatrics, may set worried parental minds slightly at ease.

The findings – taken from emergency room visits in children’s hospitals in Canada and the United States – show that IQ and intelligence is not affected in a clinically meaningful way by pediatric concussions.

The study compares 566 children diagnosed with concussion to 300 with orthopedic injuries. The children range in age from eight to 16 and they were recruited from two cohort studies. The Canadian cohort encompasses data collected from five children’s hospital emergency rooms, including Alberta Children’s Hospital in Calgary, along with those in Vancouver, Edmonton, Ottawa, and Montreal (CHU Sainte-Justine). In the Canadian hospitals, patients completed IQ tests three months postinjury.

The U.S. cohort was conducted at two children’s hospitals in Ohio, wherein patients completed IQ tests three to 18 days, postinjury.

“Obviously there’s been a lot of concern about the effects of concussion on children, and one of the biggest questions has been whether or not it affects a child’s overall intellectual functioning,” says Dr. Keith Yeates, PhD, a professor in UCalgary’s Department of Psychology and senior author of the Pediatrics paper. Yeates is a renowned expert on the outcomes of childhood brain disorders, including concussion and traumatic brain injuries.

“The data on this has been mixed and opinions have varied within the medical community,” says Yeates. “It’s hard to collect big enough samples to confirm a negative finding. The absence of a difference in IQ after concussion is harder to prove than the presence of a difference.”

Combining the Canadian and U.S. cohorts gave the Pediatrics study an abundant sample and it allowed Yeates and his co-authors – from universities in Edmonton, Montreal, Vancouver, Ottawa, Atlanta, Utah, and Ohio, along with Calgary’s Mount Royal University – to test patients with a wide range of demographics and clinical characteristics.

“We looked at socioeconomic status, patient sex, severity of injuries, concussion history, and whether there was a loss of consciousness at the time of injury,” says Yeates. “None of these factors made a difference. Across the board, concussion was not associated with lower IQ.”

The children with concussion were compared to children with orthopedic injuries other than concussion to control for other factors that that might affect IQ, such as demographic background and the experience of trauma and pain. This allowed the researchers to determine whether the children’s IQs were different than what would be expected minus the concussion.

The findings of the study are important to share with parents, says Dr. Ashley Ware, PhD, a professor at Georgia State University and lead author of the paper. While the Pediatrics research was underway, Ware was a Killam Postdoctoral Fellow at UCalgary, where Yeates was her supervisor.

“Understandably, there’s been a lot of fear among parents when dealing with their children’s concussions,” Ware says. “These new findings provide really good news, and we need to get the message to parents.”

Dr. Stephen Freedman, PhD, co-author of the paper, a professor of pediatrics and emergency medicine at the Cumming School of Medicine, agrees. “It’s something doctors can tell children who have sustained a concussion, and their parents, to help reduce their fears and concerns,” says Freedman. “It is certainly reassuring to know that concussions do not lead to alterations in IQ or intelligence.”

Another strength of the Pediatrics research is that incorporates the two cohort studies, one testing patients within days of their concussions and the other after three months.

“That makes our claim even stronger,” says Ware. “We can demonstrate that even in those first days and weeks after concussion, when children do show symptoms such as a pain and slow processing speed, there’s no hit to their IQs. Then it’s the same story three months out, when most children have recovered from their concussion symptoms. Thanks to this study we can say that, consistently, we would not expect IQ to be diminished from when children are symptomatic to when they’ve recovered.”

She adds: “It’s a nice ‘rest easy’ message for the parents.”