The apple doesn’t fall far from the tree.
Harold Joel Conn proved this adage. Conn was born in Connecticut in the late 1800s, the son of Fitchburg, Massachusetts bacteriologist Herbert William Conn. His father’s notable achievements included founding and serving as president of the Society of American Bacteriologists and discovering that typhoid fever could be spread by oysters.
The younger Conn followed in his father’s footsteps, becoming a bacteriologist in his own right and also the president of the society his parent had founded many years before. Encouraged by his father to succeed despite progressive hearing loss, Harold obtained two PhDs and became a leading scientist in his field.
One of the younger Conn’s achievements was the documentation of a gram-negative genus of bacteria called Agrobacterium. Gram-negative bacteria are so called because they do not retain the crystal violet stain that helps scientists differentiate them from the gram-positive bacteria that do hold the stain. Notable bacteria in the former category include E. coli, Chlamydia trachomatis, and plague-causing Yersinia pestis.
It took another bunch of next-generation scientists to take the research further, determining Agrobacterium’s effects on plants and its ability to manipulate genetic material. The first link discovered was that the bacterium was a causative agent of bacterial crown gall disease. This condition manifests as cankers or galls, lumps, bumps, and other protuberances that are seen on many Island oaks and other species of trees and plants.
The bacterium enters a plant from the soil into the roots or from the air through wounds in the plant. Crown gall disease develops from that incursion and usually isn’t fatal for mature and healthy trees, but can harm saplings or other vulnerable specimens. The growths can interrupt plant nutrient uptake by impeding flow through the xylem and phloem and cause weakened trees to perish. It may also allow other stressors such as winter injury, drought, or other pest species or secondary diseases to get a foot (or trunk) hold and enter through the gall’s cracks and crevices.
Agrobacterium causes crown gall disease through an ingenious method of genetic manipulation. Known as nature’s genetic engineers, these bacteria can transfer their own DNA into the genetic material of their host, altering the plant’s individual cells. This modification causes plant cells to divide and become somewhat out of control, leading to those interesting tumor-like expulsions of plant matter that we observe. The growths are not bacterial but are the out-of-control plant cells infected on a cellular level.
Normal genetic modifications occur vertically through parents providing genetic material to their offspring. These bacteria turn that notion (and the modifications) sideways by allowing horizontal gene transfer between non-related species. Because of this horizontal gene transfer ability, Agrobacteria has become an important tool for genetic engineering, having served science (or not) in the development of herbicide- and pest-resistant crops and even improved shelf life of some products. Genetically modified plants resulted from studying the gene-editing abilities of Agrobacteria.
Which led to discoveries so far-reaching as to cause an agricultural revolution. The Conn family were in at the inception of these discoveries, and following generations have continued to refine and expand the science — including Jean Conn, the third generation of bacteriologists from that scientific clan.
Just as Agrobacterium modifies its host plant, so has the Conn family modified its family science — transforming the study of bacteriology and nourishing future breakthroughs.
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.