Vampire bacteria, Tarapur reactor renewal, and uncovering Fermi’s exotic particle prophecy

How some bacteria are attracted to blood; why scientists are extending life of Tarapur nuclear plant; and how a 1949 prediction is proven true now.

Published : May 16, 2024 11:00 IST - 0 MINS READ

A Petri dish containing Salmonella bacteria.  

A Petri dish containing Salmonella bacteria.   | Photo Credit: Ted S. Warren/WSU College of Veterinary Medicine

Vampire bacteria: out for human blood

Some of the world’s deadliest bacteria seek out human blood to feed on. This newly discovered phenomenon has been named “bacterial vampirism”.

A team of scientists, led by Washington State University (WSU) researchers, found that the bacteria are attracted to the liquid part of blood, or serum, which contains nutrients the bacteria can use as food. One of the chemicals bacteria seemed to be drawn to was serine, an amino acid that is also a common ingredient in protein drinks. This finding, published in the journal eLife, provides new insights into bloodstream infections and their treatment.

“Bacteria infecting the bloodstream can be lethal,” said Arden Baylink, a WSU professor and the corresponding author for the research. “We learned that some of the bacteria that most commonly cause bloodstream infections actually sense a chemical in human blood and swim toward it.”

The team found at least three types of bacteria, Salmonella enterica, Escherichia coli, and Citrobacter koseri, are attracted to human serum. These bacteria are a leading cause of death for people who have inflammatory bowel diseases. These patients often have intestinal bleeding that can be entry points for the bacteria into the bloodstream.

Using a high-powered microscope system called the chemosensory injection rig assay, the researchers simulated intestinal bleeding with microscopic amounts of human serum and watched as the bacteria navigated towards the source. The response was rapid: it took less than a minute for the bacteria to find the serum.

As part of the study, the researchers determined that Salmonella has a special protein receptor called Tsr that enables bacteria to sense and swim towards serum. Using crystallography, they were able to view atoms of the protein interacting with serine. “By learning how these bacteria are able to detect sources of blood, in the future we could develop new drugs that block this ability,” Siena Glenn, the lead author, said.

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Units 1 and 2 of the Tarapur  Atomic Power Station in Palghar district, Maharashtra.

Units 1 and 2 of the Tarapur  Atomic Power Station in Palghar district, Maharashtra. | Photo Credit: NPCIL

TAPS units get new piping and 10 more years of life

Nuclear Power Corporation of India Limited (NPCIL) has embarked on an endeavour to replace primary recirculation piping at units 1 and 2 of the Tarapur Atomic Power Station (TAPS), in Palghar district, Maharashtra, under its ongoing programme for the life extension of TAPS.

TAPS began operations in 1969 with an initial rating of 210 MWe. Owing to various technical issues, it was derated to 160 MWe. According to NPCIL, the project addresses the significant safety concerns associated with intergranular stress corrosion cracking (IGSCC) in the existing SS 316L piping material. This refurbishment is expected to extend the lifetime of units 1 and 2 by a decade.

The IGSCC phenomenon can occur along the grain boundaries of the heat-affected zone of austenitic steel welds or the cold-worked zone and is said to be prevalent in ageing boiling water reactor plants globally. The affected critical components include the primary recirculation piping and other class-1 piping. Following regulatory approvals, NPCIL awarded the work to CORE Energy Systems Pvt. Ltd, an engineering, procurement, and construction contractor based in Mumbai. The project involves working in a radioactive zone, detailed engineering of cutting, disposal of the existing piping, and replacement with pipes made of highly specialised material.

Meanwhile, in another significant development, the Atomic Energy Regulatory Board safety review has cleared the loading of radial blanket subassemblies in the core of the 500 MWe prototype fast breeder reactor (PFBR) at Kalpakkam. Fuel loading in the PFBR began in March 2024. The reactor core loading marks an advanced stage of commissioning, a step towards making the reactor operational.

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A schematic of a nucleon-antinucleon bound state.   

A schematic of a nucleon-antinucleon bound state.   | Photo Credit: BESIII Collaboration/T. Chen

A 1949 Fermi proposal finds acceptance

High-energy collision experiments in particle accelerators have revealed several aspects of the behaviour of quarks, the subatomic building blocks of protons and neutrons. During the decay of quark clusters or aggregates, for example, exotic subatomic particles, such as tetraquarks or loosely bound mesons, have shown up (“Exotic arrival”, Frontline, May 22, 2009), appearing as resonance peaks in the mass spectra of the debris of collision experiments.

In 2013, the BESIII Collaboration at the Beijing Electron Positron Collider observed one such peak in the decay of a particle called J/psi that is 3.5 times heavier than a proton (mass: 940 MeV). This was thought to be a new short-lived meson—a quark-antiquark bound state—and was named X(1840), the number denoting its mass in million electronvolts (MeV).

The existence of this peak has now been confirmed. But analysis of much more data than a decade earlier—with 50 times more decay events—has revealed that the earlier peak was actually two overlapping peaks with a lower secondary peak at 1,880 MeV. The observation has a high degree of statistical significance too, thus confirming the existence of a second new exotic particle. It has been labelled X(1880). The work was published in a recent issue of Physical Review Letters.

The proximity of the mass of these two particles to twice the proton mass is suggestive of nucleon-antinucleon bound states, an idea that has a long history. Enrico Fermi and C.N. Yang proposed it in 1949, long before the birth of the quark model. Thus, the behaviour of particles in this mass regime can help physicists understand the bound states of protons and other particles with similar masses.

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