This pandemic year has seen us confined to our homes and restricted from travelling the world. Not so for some microscopic bacteria in the ocean: Throughout the globe, they partner up with clams from the family Lucinidae, which live unseen in the sand beneath the shimmering blue waters of coastal habitats. This partnership is the clams’ passport to their extensive global reach. The bacteria can also travel a long way. According to research by scientists from the Max Planck Institute for Marine Microbiology in Bremen and the University of Vienna now published in the Proceedings of the National Academy of Sciences, the bacterial symbionts living in lucinid gills can travel the world without borders.

The Lucinidae family, lucinids for short, comprises approximately 500 living species of bivalves. They are at least 400 million years old, according to fossil records, and have managed to colonize a wide variety of habitats, from beautiful beaches to the abyssal depths untouched by the sun over a kilometer below the sea surface. Their ability to thrive in a wide variety of habitats is made possible by their ‘partner in crime’, a sulfur-oxidizing bacterial symbiont that utilizes hydrogen sulfide, better known as ‘rotten egg gas’, as an energy source to power primary production. This process is not unlike photosynthesis used by plants, yet not dependent on sunlight, and generates enough sugars to feed both the symbiont and the lucinids themselves.

Striking up partnerships from near or far

Finding a suitable partner out in the wild is a matter of life and death for lucinids. They have to pick up their bacterial partners at a very early life stage when they settle in the sediment after their larval stage. From this time on, they rely on their bacterial symbionts for nutrition. However, bacterial cells are miniscule and the oceans are awash with a multitude of possible candidates. Typically, animals that rely so heavily on bacteria are expected to strike up partnerships with local residents. These microbes are likely to work best under the unique conditions of their local habitats. A new study based on metagenomic analyses of symbiotic bacteria in lucinids now reveals that this is not always the case: Some bacterial symbionts travel the globe and are true cosmopolitans.

Globally distributed symbionts

“Using state-of-art DNA-sequencing and genome assembling, we discovered that a single bacterial symbiont species was the most abundant symbiont in eight lucinid species spanning three oceans — the Atlantic, Pacific and Indian Oceans — across the tropics of both hemispheres,” said Laetitia Wilkins from the Max Planck Institute for Marine Microbiology in Bremen, Germany, shared first author of the publication together with Jay Osvatic from the University of Vienna, Austria. “These symbionts are virtually all over the place.” No other known symbiont is so successful at dispersal and establishing symbioses with lucinids, the researchers report. They named it Candidatus Thiodiazotropha taylori — “to acknowledge the wisdom of John Taylor from the Natural History Museum in London, who has devoted 25 years of his

The first large study showing that leisure time physical activity and occupational physical activity have opposite, and independent, associations with cardiovascular disease risk and longevity is published today in European Heart Journal, a journal of the European Society of Cardiology (ESC).

“We adjusted for multiple factors in our analysis, indicating that the relationships were not explained by lifestyle, health conditions or socioeconomic status,” said study author Professor Andreas Holtermann of the National Research Centre for the Working Environment, Copenhagen, Denmark.

The World Health Organization (WHO) recommends physical activity during both recreation and work to improve health.* Previous studies have suggested that occupational activity is related to an increased risk for heart disease and mortality but have been too small to fully explain whether this was due to the manual work or because employees had unhealthy lifestyles or low socioeconomic status (e.g. low level of education).

This study included 104,046 women and men aged 20-100 years from the Copenhagen General Population Study with baseline measurements in 2003-2014. Participants completed questionnaires about activity during leisure and employment and were categorised as low, moderate, high, or very high activity for each.

During a median follow-up of 10 years, there were 9,846 (9.5%) deaths from all causes and 7,913 (7.6%) major adverse cardiovascular events (MACE, defined as fatal and nonfatal myocardial infarction, fatal and non-fatal stroke, and other coronary death).

Compared to low leisure time physical activity, after adjustment for age, sex, lifestyle, health, and education, moderate, high, and very high activity were associated with 26%, 41%, and 40% reduced risks of early death, respectively. In contrast, compared to low work activity, high and very high activity were associated with 13% and 27% increased risks of death, respectively.

Similarly, after adjustments, compared to low leisure activity, moderate, high, and very high levels of leisure activity were associated with 14%, 23%, and 15% reduced risks of MACE, respectively. Compared to low work activity, high and very high levels were associated with 15% and 35% increased risks of MACE, respectively.

Professor Holtermann said: “Many people with manual jobs believe they get fit and healthy by their physical activity at work and therefore can relax when they get home. Unfortunately, our results suggest that this is not the case. And while these workers could benefit from leisure physical activity, after walking 10,000 steps while cleaning or standing seven hours in a production line, people tend to feel tired so that’s a barrier.”

While the study did not investigate the reasons for the opposite associations for occupational and leisure time physical activity, Professor Holtermann said: “A brisk 30-minute walk will benefit your health by raising your heart rate and improving your cardiorespiratory fitness, while work activity often does not sufficiently increase heart rate to improve fitness. In addition, work involving lifting for several hours a day increases blood pressure for many hours, which is linked with heart disease risk, while short bursts of intense physical activity during leisure raises blood pressure only briefly.”

Professor Holtermann’s vision is