Enlarge / BARCELONA, SPAIN - 2021/10/02: Spanish tattoo artist Oscar Garcia works on a man, during the Expo. Fira de Barcelona hosts the XXIV edition of the Barcelona Tattoo Expo where tattoo artists from Spain and other countries exhibit tattoos and tattoo material such as ink, needles and special machinery for tattoo work. (Photo by Ramon Costa/SOPA Images/LightRocket via Getty Images)

The Food and Drug Administration has been warning for years that some tattoo inks are brimming with bacteria—a large assortment that, when injected into your skin, can cause inflammatory reactions, allergic hypersensitivity, toxic responses, and, of course, straight-up infections. And, worse yet, the labels that say the inks are sterile are not reliable.

But, a recent recall of three tattoo pigments from the same manufacturer does a good job of illustrating the FDA's concerns. The water-based inks, all from Sierra Stain, had a bizarre array of bacteria, which were found at high levels, according to FDA testing.

One ink product—described as "Carolina Blue"—offered a microbial menagerie, with six odd species identified. They included a bacterium that often dwells in the gastrointestinal system and can inflame the mucosal lining of the intestines (Citrobacter braakii), a water-borne bacterium (Cupriavidus pauculus), and several that cause opportunistic infections (Citrobacter farmer, Achromobacter xylosoxidans, Ochrobactrum anthropi, and Pseudomonas fluorescens). These are bacteria that don't typically go about attacking humans but will if the conditions are right, including when they find themselves inside a human with a compromised immune system.

Enlarge / A recall notice is posted next to Boar's Head meats that are displayed at a Safeway store on July 31, 2024, in San Rafael, California. (credit: Getty | Justin Sullivan)

A third person has died in a nationwide bacterial outbreak linked to Boar's Head brand deli meats. Last week, the company recalled more than 7 million pounds of its meats, which was in addition to a recall of over 200,000 pounds of meat from July 26. In all, 71 types of products made between May 10, 2024, and July 29, 2024, and sold nationwide have been recalled.

According to an update Thursday from the Centers for Disease Control and Prevention, the outbreak has now sickened a total of 43 people, an increase from 34 last week. There have been 43 hospitalizations, up from 33 last week. The illnesses are reported from 13 states. The three deaths in the outbreak include one from Illinois and one from New Jersey, and the newly reported death is from Virginia. The CDC expects the tally of illnesses so far to be a significant undercount of actual cases, and additional states may be affected.

The illnesses in the outbreak are caused by Listeria monocytogenes, a foodborne bacterium that is particularly dangerous to people who are pregnant, people age 65 years or older, and people who have weakened immune systems. In these high-risk groups, the bacteria are more likely to move beyond the gastrointestinal system to cause an invasive infection called listeriosis. During pregnancy, listeriosis can cause miscarriage, stillbirth, premature delivery, or a life-threatening infection in newborns. For non-pregnant people who develop listeriosis, nearly 90 percent require hospitalization, and 1 in 6 die.

Enlarge / This is an intact phage. A tailocin looks like one of these with its head cut off. (credit: iLexx)

Long before humans became interested in killing bacteria, viruses were on the job. Viruses that attack bacteria, termed "phages" (short for bacteriophage), were first identified by their ability to create bare patches on the surface of culture plates that were otherwise covered by a lawn of bacteria. After playing critical roles in the early development of molecular biology, a number of phages have been developed as potential therapies to be used when antibiotic resistance limits the effectiveness of traditional medicines.

But we're relative latecomers in terms of turning phages into tools. Researchers have described a number of cases where bacteria have maintained pieces of disabled viruses in their genomes and converted them into weapons that can be used to kill other bacteria that might otherwise compete for resources. I only just became aware of that weaponization, thanks to a new study showing that this process has helped maintain diverse bacterial populations for centuries.

Evolving a killer

The new work started when researchers were studying the population of bacteria associated with a plant growing wild in Germany. The population included diverse members of the genus Pseudomonas, which can include plant pathogens. Normally, when bacteria infect a new victim, a single strain expands dramatically as it successfully exploits its host. In this case, though, the Pseudomonas population contained a variety of different strains that appeared to maintain a stable competition.

Enlarge (credit: Timothy Hearsum)

Fritz Haber: good guy or bad guy? He won the Nobel Prize in Chemistry in 1918 for his part in developing the Haber-Bosch process, a method for generating ammonia using the nitrogen gas in air. The technique freed agriculture from the constraint of needing to source guano or manure for nitrogen fertilizer and is widely credited for saving millions from starvation. About half of the world’s current food supply relies on fertilizers made using it, and about half of the nitrogen atoms in our bodies can be traced back to it.

But it also allowed farmers to use this newly abundant synthetic nitrogen fertilizer with abandon. This has accentuated agriculture’s role as a significant contributor to global warming because the emissions that result from these fertilizers is a greenhouse gas—one that has a warming potential almost 300 times greater than that of carbon dioxide and remains in the atmosphere for 100 years. Microbes in soil convert nitrogen fertilizer into nitrous oxide, and the more nitrogen fertilizer they have to work with, the more nitrous oxide they make.

Agriculture also leaks plenty of the excess nitrogen into waterways in the form of nitrate, generating algal blooms that create low-oxygen ‘dead zones’ where no marine life can live.