IMAGE: NANO CREATIVE/SCIENCE SOURCE240 15 APRIL 2022 • VOL 376 ISSUE 6590 science.org SCIENCEBy Jolanta PrywerB
iogenic crystals are crystals that grow
inside or under the influence of living
organisms. These crystals are incred-
ibly diverse, and the process of their
growth is extremely complex. Despite
their ubiquity, only several dozen
biogenic crystals have been identified and
studied. On page 312 of this issue, Avrahami
et al. ( 1 ) present studies of coccoliths, which
are micrometer-sized calcite (CaCO 3 ) single
plates formed by coccolithophores, a type
of single-celled algae. The coccolithophores
form around themselves a calcite shell
called a coccosphere, which is composed of
dozens of coccolith plates. Before discuss-ing the most important and specific aspects
of this study, it is worth exploring the di-
verse world of biogenic crystals.
The habits of biogenic crystals—defined
as the characteristic external appearances
of the crystal—are incredibly diverse. They
range from simple regular prismatic crystals
through spherical aggregates to individual
needles with sharp points. In the case of cal-
cium oxalate [CaC 2 O 4 ·(H 2 O)x] crystals found
in over 200 plant families ( 2 ), their habits
and their presence in specific plant tissues
determine their functions. For example,
needle-like crystals found in leaves may
play a defensive role against herbivores ( 3 ).
Sometimes these needles have grooves that
can help transport toxins to the nibbledparts of the plant. Biogenic crystals can
also be used to help manage nutrients and
growth. For example, calcium oxalate crys-
tals, found in plants, are thought to serve
as a calcium reservoir for maintaining a
proper ionic balance ( 4 ). The same crystals
may also be used to help control the level
of solubility for potentially toxic substances
such as oxalic acid.
There also exist other, perhaps more
peculiar, uses for biogenic crystals. For
example, magnetotactic bacteria produce
nanometer-sized magnetic crystals in their
intracellular membrane vesicles ( 5 ) to help
orient themselves using Earth’s magnetic
field and navigate toward certain aquatic
environments that favor their survival ( 6 ).CRYSTALLOGRAPHYThe fascinating world of biogenic crystals
PERSPECTIVES
The diverse properties of these crystals may lead to a variety of applications
INSIGHTS