Terrestrial vertebrates have repeatedly evolved elongate, limbless body plans, which require them to move using drastically different types of locomotion than their limbed relatives do. Despite their superficially simple body plans, snakes have evolved remarkable behavioral and ecological flexibility, moving in at least a dozen distinct ways and inhabiting diverse habitats. We still have much to learn about how a superficially simple body plan can generate extreme diversity, but external similarity suggests a huge effect of the underlying axial musculoskeletal system and/or behavior. Behavioral evolution can occur rapidly and dramatically alter relationships between morphology and function. Characterizing the nature and potential sources of variation has implications for ecology, since the degree of flexibility in locomotor behavior could influence ability to expand into new habitats, or to cope with a changing one. This seminar talk will include a review of snake locomotor diversity, plus results of research on the evolution of behavioral and morphological traits that have helped generate such diversity. That research has involved a variety of approaches, spanning fieldwork to museum work to modelling, plus single-species and phylogenetic comparative methods.

 

Hosted by Dr. Mendelson

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What’s in a name? A lot, actually.

For the scientific community, names and labels help organize the world’s organisms so they can be identified, studied, and regulated. But for bacteria, there has never been a reliable method to cohesively organize them into species and strains. It’s a problem, because bacteria are one of the most prevalent life forms, making up roughly 75% of all living species on Earth.

An international research team sought to overcome this challenge, which has long plagued scientists who study bacteria. Kostas Konstantinidis, Richard C. Tucker Professor in the School of Civil and Environmental Engineering at the Georgia Institute of Technology, co-led a study to investigate natural divisions in bacteria with a goal of determining a scientifically viable method for organizing them into species and strains. To do this, the researchers let the data show them the way.

Their research was published in the journal Nature Communications.

“While there is a working definition for species and strains, this is far from widely accepted in the scientific community,” Konstantinidis said. “This is because those classifications are based on humans’ standards that do not necessarily translate well to the patterns we see in the natural environment.”

For instance, he said, “If we were to classify primates using the same standards that are used to classify E. coli, then all primates — from lemurs to humans to chimpanzees — would belong to a single species.”

There are many reasons why a comprehensive organizing system has been hard to devise, but it often comes down to who gets the most attention and why. More scientific attention generally leads to those bacteria becoming more narrowly defined. For example, bacteria species that contain toxic strains have been extensively studied because of their associations with disease and health. This has been out of the necessity to differentiate harmful strains from harmless ones. Recent discoveries have shown, however, that even defining types of bacteria by their toxicity is unreliable.

“Despite the obvious, cornerstone importance of the concepts of species and strains for microbiology, these remain, nonetheless, ill-defined and confusing,” Konstantinidis said.

The research team collected bacteria from two salterns in Spain. Salterns are built structures in which seawater evaporates to form salt for consumption. They harbor diverse communities of microorganisms and are ideal locations to study bacteria in their natural environment. This is important for understanding diversity in populations because bacteria often undergo genetic changes when exposed in lab environments.

The team recovered and sequenced 138 random isolates of Salinibacter ruber bacteria from these salterns. To identify natural gaps in genetic diversity, the researchers then compared the isolates against themselves using a measurement known as average nucleotide identity (ANI) — a concept Konstantinidis developed early in his career. ANI is a robust measure of relatedness between any two genomes and is used to study relatedness among microorganisms and viruses, as well as animals. For instance, the ANI between humans and chimpanzees is about 98.7%.

The analysis confirmed the team’s previous observations that microbial species do exist and could be reliably described using ANI. They found that members of the same species of bacteria showed genetic relatedness typically ranging from 96 to 100% on the ANI scale, and generally less than 85% relatedness with members of other species.

The data revealed a natural gap in ANI values around 99.5% ANI within the Salinibacter ruber species that could be used to differentiate the species into its various strains. In a companion paper published in mBio, the flagship journal of the American Society for Microbiology, the team examined about 300 additional bacterial species based on 18,000 genomes that had been recently sequenced and become available in public databases. They observed similar diversity patterns in more than 95% of the species.

“We think this work expands the molecular toolbox for accurately describing important units of diversity at the species level and within species, and we believe it will benefit future microdiversity studies across clinical and environmental settings,” Konstantinidis said.

The team expects their research will be of interest to any professional working with bacteria, including evolutionary biologists, taxonomists, ecologists, environmental engineers, clinicians, bioinformaticians, regulatory agencies, and others. It is available online through Konstantinidis’ website and GitHub to facilitate access and use by scientific and regulatory communities.

“We hope that these communities will embrace the new results and methodologies for the more robust and reliable identification of species and strains they offer, compared to the current practice,” Konstantinidis said.

 

Note: Tomeu Viver and Ramon Rossello-Mora from the Mediterranean Institutes for Advanced Studies also led the research. Additional researchers from the Georgia Institute of Technology, University of Innsbruck, University of Pretoria, University of Las Palmas de Gran Canaria, University of the Balearic Islands, and the Max Planck Institute also contributed. 

Citation: Viver, T., Conrad, R.E., Rodriguez-R, L.M. et al. Towards estimating the number of strains that make up a natural bacterial population. Nat Commun 15, 544 (2024).

DOI: https://doi.org/10.1038/s41467-023-44622-z

Funding: Spanish Ministry of Science, Innovation and Universities, European Regional Development Fund, U.S. National Science Foundation.

Emerging new phenotypes and clinical presentations in neurodegenerative diseases challenge the current paradigm of homotypic (single-protein) amyloids and implicate the possibility of heterotypic amyloid aggregates as the underlying cause. Our incomplete understanding is apparent when considering an increasing number of pathologies that exhibit distinct phenotypes and clinical presentations correlating better with colocalized cytoplasmic amyloid inclusions of different amyloid proteins. In particular, both a-synuclein (aS) and TDP-43 proteins are observed in pathologies such as limbic predominant age-related TDP43 encephalopathy neuropathological changes (LATE-NC), Lewy body dementia (LBD), and multiple system atrophy (MSA). Aberrant aggregates of the two proteins also form the hallmarks of frontotemporal lobar degeneration (FTLD) and Parkinson’s disease. TDP-43 is present in two distinct phases in physiology and pathology. During stress, TDP-43 undergoes liquid-liquid phase separation (LLPS) with RNA and partitions into RNA-rich foci called stress granules in the cytoplasm, while in pathology, the protein forms toxic cytoplasmic insoluble amyloid aggregates. Our investigations reveal that aS and TDP-43 synergistically interact with each other to form distinct neurotoxic heterotypic aggregates that are dependent on TDP-43 phase behavior. In homogenous phase conditions, aS and prion-like c-terminal domain (PrLD) of TDP43 synergistically co-aggregate toward heterotypic fibrils containing both proteins, while in demixed solutions containing TDP43-RNA droplets, aS emulsifies the liquid droplets to promote heterotypic amyloid aggregates. Together these data suggest aS-TDP-43 heterotypic amyloids as potential molecular entities for distinct phenotype emergence in some neurodegenerative diseases.
 
 
Hosted by Matthew Torres

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Corals are foundational for ocean life. Known as the rainforests of the sea, they create habitats for 25% of all marine organisms, despite only covering less than 1% of the ocean’s area. 

Coral patches the width and height of basketball arenas used to be common throughout the world’s oceans. But due to numerous human-generated stresses and coral disease, which is known to be associated with ocean sediments, most of the world’s coral is gone.

“It’s like if all the pine trees in Georgia disappeared over a period of 30 to 40 years,” said Mark Hay, Regents’ Chair and the Harry and Anna Teasley Chair in Environmental Biology in the School of Biological Sciences at the Georgia Institute of Technology. “Just imagine how that affects biodiversity and ecosystems of the ocean.”

In first-of-its-kind research, Hay, along with research scientist Cody Clements, discovered a crucial missing element that plays a profound role in keeping coral healthy — an animal of overlooked importance known as a sea cucumber.

Read about how they figured it out at Georgia Tech Research News.

Are you ready for an evening that blends inspiration, connection, and shared experiences? Join us for a memorable evening of growth and camaraderie at the College of Sciences Student and Alumni Leadership Dinner.

Registration is required. Students and alumni are encouraged to register through CareerBuzz on the Georgia Tech Career Center webpage. Faculty and staff, please register here.

For more information or inquiries, reach out to the College of Sciences Career Educator, James Stringfellow, at james.stringfellow@gatech.edu. Please include "Leadership Dinner" in the subject line when reaching out.

Event Highlights:

  • Connect with fellow College of Sciences students and alumni
  • Engage in meaningful small group discussions
  • Hear inspiring stories and insights from accomplished alumni
  • Enjoy delightful music and dinner
  • Ignite your passion and drive for success

Event Details:

Date: March 12th, 2024
Time: 6:00 PM - 8:00 PM
Location: Georgia Tech Alumni House
Attire: Business casual attire is recommended.

Registration: To secure your spot at this exclusive event, please register through CareerBuzz on the Georgia Tech Career Center webpage.

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Place yourself in the performer's shoes in this interactive workshop following the screening of Piece of Mind: Dementia - an artistic performance highlighting scientific research and lived experiences of dementia. Together, Piece of Mind performers and attendees will dissect specific scenes from the film, discussing the creative process and delving into the underlying information, emotions and metaphors through creative movement. This workshop is hosted by Montreal-based circus and dance artists and scientists/clinicians/advocates from local Atlanta institutes.

Presented by Georgia Tech, Emory University, National Circus School of Montreal, and Centre for Circus Arts Research, Innovation and Knowledge Transfer (CRITAC)

 

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The human hand possesses far more superior dexterity than our mammalian ancestors and our non-human primate cousins. Critically, individuated finger control, supported by the evolutionary newer neural circuits, allows us to break the more primitive power grip to various fine-tuned subtle finger movements and hand postures to achieve a dazzling array of manual skills, from a mundane task of tying the shoelace to the feat of playing Bach’s Partitas. How we achieve this remarkable level of dexterity and what the biological roots are is yet to be elucidated. In this talk I will present recent work from my research team in understanding the neural and behavioral complexities of finger control. Using 3-dimensional isometric fingertip forces recorded simultaneously from all five fingers, we show that finger enslavement patterns during individuated finger control after stroke present a loss of behavior complexity, which is dissociable from the intrusion of non-selective flexor bias, indicating differential neural pathways supporting the two. Lastly, I will also discuss how finger individuation may participate in multi-finger manipulations and exploratory behaviors in motor skill learning and its biological and rehabilitation implications.

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Mammals learn a large repertoire of novel actions by refining variable movements into precise skills. The brain achieves this by assigning credit to movements that led to desired outcomes. Even for simple actions such as reaching to a spatial target, the brain could assign credit to the direction, endpoint target location, speed, etc. As such, different movement strategies may emerge across individuals, depending on what is assigned with credit.

My goal is to dissect the sensorimotor areas controlling different aspects of these movements, and probe what determines the learning and control of different reach strategies. I developed a behavior task in which head-fixed mice generate exploratory forelimb trajectories with a joystick and are rewarded when they hit a hidden target in the workspace. As mice learn, they refine their target reaches which become less variable in direction, tortuosity, speed, and targeting precision. I show that different aspects of the reach such as direction or speed are learned and controlled through distinct cortical and thalamic networks. For instance,
sensorimotor cortex is required to generate reaches with high directional variability across different positions of the workspace, while a specific nucleus of thalamus is required to refine the overall reach direction.

But what reach strategies are mice learning? By relocating the start position in a small number of probe trials I discovered that some animals learned a direction-based strategy (move in the same initial direction from new starts), while others learned an endpoint-based strategy (guide the joystick into the target from new starts, adjusting their direction). Which strategy an individual animal learned correlated with the degree of spatial directional variability during exploration, the aspect of the reach controlled by cortex. This correlation is also recapitulated by model-free reinforcement learning agents trained in a similar task. Overall, these findings suggest that the sensorimotor system learns different control strategies by exploring and reinforcing certain movement aspects during learning, and that these aspects are generated by distinct circuits.

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The burgeoning field of ‘cancer-neurobiology’ centers on studying interactions among cancer, the nervous system, and cancer treatment. My recent multi-scale studies provide the first evidence that cancer and chemotherapy interact non-linearly to exacerbate neurologic disorders experienced by patients. In this talk, I will present evidence that multiple loci throughout the central- and peripheral nervous systems jointly contribute to maladaptive phenotypes. I will share results of my ongoing studies that integrate biophysical modeling, in vivo electrophysiology, kinematic evaluation, spatially informed omics, and in vivo gene knockdown to identify underlying molecular mechanism(s). Serendipitously, my studies also identified multiple pathways that link neurons to cancer. Cancer is suspected to subvert and repurpose core neuronal mechanisms to its advantage, yet little is known. I will conclude by sharing a new theme of my research program aimed at defining how these two diverse biological processes converge, with a particular interest in understanding how the nervous system responds to and influences cancer.

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Physiological mechanisms underly various aspects of animal performance, ranging from the response of individuals to environmental stressors to larger-scale migratory movements and collective behaviours. Physical factors, such as O2 level, temperature, water velocity and flow dynamics, underpin most aspects of animal locomotion, from fine-scale maneuvers to long-distance migrations. Building functional links from physiology to broader-scale biological and oceanic patterns is desirable and impactful, but faces many technological and conceptual challenges. Using a multi-faceted approach and several fish species as models, my research program aims to bridge this gap by studying physiological performance curves: how physiological performance responds to a broad range of physical and biotic factors. An individual-based hypoxic performance curve quantified the constraint of low O2 on the energetics of the fish, and the curve is plastic in European bass (D. labrax). The thermal performance curve showed that a cold-water species (rainbow trout, O. mykiss) can be acclimated to above 18 °C, the daily maxima recommended by U.S. Environmental Protection Agency, but the acclimation potential has an upper limit indicated by cardiac distress. Schooling behaviour of giant danio (D. aequipinnatus) fish downshifted their locomotor performance curve compared to a solitary individual, showing dramatic (~60%) energy saving in both laminar and turbulent flows by changing their collective kinematics. These physiological performance curves form a framework for generating a physiological performance space. Studying physiological performance spaces by integrating across molecular, organismic and ecological levels has great promise for generating functional links between physiology and broader-scale biological patterns.

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