“Bar codes may check out next” (SN: 4/24/10, p. 14) describes a new ink that would enable a full grocery cart to be quickly checked out electronically. Hurrah? Undoubtedly the amount of radio frequency per package would be minimal. However, if much of our food were handled that way, and people used it for years, the exposure might be significant. What would be the effect on our health and the environment?

We thought plastics were wonderful; they are, but are now in our blood and mothers’ milk. Flame retardants have their own litany of problems, including, as you note, appearing in falcon eggs (SN: 4/24/10, p. 12). Cell phones are fabulous, but what are they doing to children’s brains? How many wonderful inventions, thoughtlessly applied, have “unintended consequences”? Before this new ink is used, surely some cautious research is warranted.

Lesley Alexander, Santa Barbara, Calif.

More correct correction
In case 87 readers haven’t already
pointed it out, the “Correction” in the
May 8 issue (SN: 5/8/10, p. 32) has
another mistake: “… Jupiter’s larg-
est moon, Io.” Of course, Ganymede is
Jupiter’s largest moon, and Callisto is
larger than Io as well.
K.A. Boriskin, Bellingham, Mass.

The reader is correct: Io is the third largest Jovian moon. — Ron Cowen

Twins not immune to differences
Regarding the article “Identical twins
differ at gut level” (SN: 4/24/10, p. 9): It
seems that many researchers fail to take
into account the unique genetics of the
acquired immune system when studying
identical twins. Although each identical
twin inherits the same germ line DNA,
both B and T cells not only rearrange
that DNA but also add (and delete) non-
genome encoded nucleotides to genes
to make antibodies or T cell receptors,
independently of antigen exposure.
Have the authors considered the pos-
sibility of immune-driven variations in
gut microbe diversity in identical twins?
Jennifer L. Bankers-Fulbright,
Minneapolis, Minn.

How the immune system and the gut microbiome shape each other is a good question “and one we are fascinated by,” says study author Jeffrey Gordon of Washington University School of Medicine in St. Louis. All the details aren’t in, but he says it is clear that changes in the immune system can alter the gut microbiota, and vice versa. “These are reciprocal and dynamic relationships,” which are now under intensive study by his and several other research groups, Gordon says. — Laura Sanders

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