Luallen Lab members pose in their lab at SDSU. Inset: Microscope image of Bordetella atropi (pink lines) infecting roundworm intestine (green). Credit: San Diego State University
Like something out of a horror movie, a new way that one type of bacteria invades tissue within a living organism has been identified by biologists from San Diego State University.
The study, published in Nature Communications, describes how a new species of bacteria, Bordetella atropi, invades its roundworm host. The name which comes from the Greek fate Atropos responsible for cutting the threads of life, is apt because the bacteria transforms into a long thread, growing up to 100 times the usual size of one bacterium in the span of 30 hours without dividing.
By altering the genes of B. atropi, the research team discovered that this invasive threading relies on the same genes and molecules that other bacteria use when they are in a nutrient-rich environment. However, these other bacteria only use this pathway to make subtly larger cells, whereas the B. atropi bacteria grows continuously.
Other bacteria often transform into threads, called filamentation, in response to dangerous environments or DNA damage. This lets them continue to grow in size, but delay cell division until they repair the damage inflicted by the stress.
Here, however, the researchers were the first to observe filamentation as a way of spreading from cell to cell in a living organism for a purpose other than the stress response. They believe that instead the new species is invading the host cells, detecting this rich environment and triggering filamentation in order to quickly infect more cells and access additional nutrients for their growth.
“We went from finding the worm in the ground, finding the bacteria, and carrying it all the way to the molecular mechanism of how the bacteria infects the worm,” explained Robert Luallen, biology professor and principal investigator of the study. “We’re seeing things that no one’s ever seen before.”
Though B. atropi does not infect humans, it is possible that human pathogens may also make use of its spreading mechanism. Separately, the nutrient-induced filamentation process might be used by other bacteria to form biofilms, which can coat the tubing of catheters and lead to complications for patients.
In a study published in Influenza and Other Respiratory Viruses, researchers were able to detect SARS-CoV-2 viral RNA in droplets from the exhaled breaths and coughs of COVID patients.
COVID is assumed to be transmitted mainly by respiratory droplets. However, probable aerosol transmission has been reported to occur under certain conditions. The researchers sought to address the lack of information on viral load in exhaled breath samples,as well as the size and concentration of exhaled endogenously generated droplets in relation to viral load. Additionally, the relationship between the viral load in upper airway diagnostic samples and aerosol samples needed to diagnose. For the study, researchers analysed exhalations by two different methods during 20 normal breaths, 10 airway opening breaths (which involves deep inhalation followed by relaxed exhalation), and 3 coughs.
PCR detection of SARS-CoV-2 RNA in aerosols was possible in 10 out of 25 participants. Viral RNA presence in aerosol was mainly detected in cough samples (8 samples), but also in normal breaths (4 samples) and in airway opening breaths (3 samples).
“Our data confirm findings from other researchers that SARS-CoV-2 can be detected in aerosol particles < 5µm and highlight the small amount of exhaled aerosol needed for detection. Of specific interest were findings from the airway opening maneuver, which is thought to generate particles mainly from the small airways,” said lead author Emilia Viklund, PhD student at the University of Gothenburg, in Sweden. “COVID causes a lot of damage in this region, and it would be of great interest to further explore the amount of exhaled virus and the course of disease, as well as the infectious potential of exhaled virus.”
A study into the genetics of acne revealed 29 regions of the genome that underpin the condition, which could offer potential new treatment targets and may also help clinicians identify individuals at high risk of severe disease.
A common skin condition, acne is estimated to affect 80% of adolescents, with common features including spots and cysts, pigment changes and scarring. The face is the most common site, with the chest and back also frequently involved. The negative psychological consequences of acne are seen in all ages, but are of particular concern for many adolescents.
The research, published in Nature Communications, analysed nine genome wide association study datasets from patients around the world. These studies involved scanning the whole genomes of 20 165 people with acne and 595 231 without. The study identified 29 new genetic variants that are more common in people with acne. It also confirmed 14 of the 17 variants already known to be associated with the condition, which brings the total number of known variants to 46.
Professor Catherine Smith at St John’s Institute of Dermatology at Guy’s and St Thomas’ said: “Despite major treatment advances in other skin conditions, progress in acne has been limited. As well as suffering from the symptoms of acne, individuals describe consequent profound, negative impacts on their psychological and social wellbeing. It’s exciting that this work opens up potential avenues to find treatments for them.”
A number of genes associated with acne were identified, and are also linked to other skin and hair conditions. The team believe this will help to understand the causes of acne, which could be a mix of factors.
“We know that the causes of acne are complicated, with a mix of biological factors such as genetics and hormones, and environmental factors,” said Professor Michael Simpson at King’s College London. “Understanding the genetics of the condition will help us to disentangle some of these causes, and find the best way to treat the condition. This is a really promising area for further study, and opens up a lot of avenues for research.”
The study also uncovered a link between the genetic risk of acne and disease severity. Individuals with the highest genetic risk are more likely to have severe disease. While further research is required, this finding raises the potential to identify individuals at risk of severe disease for early intervention.
In a world first, Michel Roccati, a man with a completely severed spinal cord was able to walk again outside the lab with the help of a portable electrical stimulation system that causes his legs to take a step in conjunction with his intention to move and a walker to steady him.
This was a further development of a technology that in 2018 helped David M’zee, who had been left paralysed by a partial spinal cord injury suffered in a sports accident, to walk again. A research team led by Professors Grégoire Courtine, at École Polytechnique Fédérale de Lausanne (EPFL) and Jocelyne Bloch, at Lausanne University Hospital (CHUV) had developed an electrical stimulation system to help people with spinal cord injuries walk again.
They had wanted to see if electrodes could stimulate movement in the parts of the spine damaged so badly that signals no longer reach the nervous system from the brain. That pioneering study was detailed in Nature and Nature Neuroscience. Thanks to the electrodes making up for the weakness of the signals in his damaged spinal cord, M’zee was able to voluntarily move his legs and could walk several hundred metres at a time, sometimes without the aid of the rails on the treadmill.
Now a new milestone has just been reached with the technology, and the research team enhanced their system with more sophisticated implants controlled by advanced software. These implants can stimulate the region of the spinal cord that activates the trunk and leg muscles. Thanks to this new technology, three patients with complete spinal cord injury were able to walk again outside the lab. “Our stimulation algorithms are still based on imitating nature,” said Prof Courtine. “And our new, soft implanted leads are designed to be placed underneath the vertebrae, directly on the spinal cord. They can modulate the neurons regulating specific muscle groups. By controlling these implants, we can activate the spinal cord like the brain would do naturally to have the patient stand, walk, swim or ride a bike, for example.”
On a cold, snowy day last December, Michel Roccati – an Italian man who became paralysed after a motorcycle accident four years earlier – braved the icy wind to try out the system outdoors, in central Lausanne. He had recently undergone the surgical procedure in which Prof Bloch placed the new, implanted lead on his spinal cord.
Scientists attached two small remote controls to Michel’s walker and connected them wirelessly to a tablet that forwards the signals to a pacemaker in Michel’s abdomen. The pacemaker in turn relays the signals to the implanted spinal lead that stimulates specific neurons, causing Michel to move. Grasping the walker, Michel pressed a button corresponding to either the left or right leg with the firm intention of taking a step forward, and his feet rose and fell in short steps.
“The first few steps were incredible – a dream come true!” he says. “I’ve been through some pretty intense training in the past few months, and I’ve set myself a series of goals. For instance, I can now go up and down stairs, and I hope to be able to walk one kilometre by this spring.”
Two other patients have also successfully tested the new system, which is described in Nature Medicine. “Our breakthrough here is the longer, wider implanted leads with electrodes arranged in a way that corresponds exactly to the spinal nerve roots,” said Bloch. “That gives us precise control over the neurons regulating specific muscles.” Ultimately, it allows for greater selectivity and accuracy in controlling the motor sequences for a given activity.
While extensive training is necessary for patients to get comfortable using the device, the speed and scope of rehabilitation is amazing. “All three patients were able to stand, walk, pedal, swim and control their torso movements in just one day, after their implants were activated!” said Prof Courtine. “That’s thanks to the specific stimulation programs we wrote for each type of activity. Patients can select the desired activity on the tablet, and the corresponding protocols are relayed to the pacemaker in the abdomen.”
While the progress achievable in a single day is astonishing, the gains after several months are even more impressive. The three patients followed a training regimen based on the stimulation programs and were able to regain muscle mass, move around more independently, and take part in social activities like having a drink standing at a bar. What’s more, because the technology is miniaturized, the patients can perform their training exercises outdoors and not only inside a lab.
Presently there is one key limitation, Prof Bloch said: “We need at least six centimetres of healthy spinal cord under the lesion. That’s where we implant our electrodes.”
As for Roccati, after nine months of Lausanne-based rehab, he now lives independently in Italy. “I continued rehab at home, working alone, with all the devices,” he said. “And I see improvements every day.”
