Studies Conflict on Spores’ Need for Protein Synthesis

Different assays lead to opposing conclusions on bacterial spores’ requirements during germination.

By Kerry Grens | December 1, 2016

Germination: Spores of Bacillus subtilis incubated in germination solution for 30 minutes turn dark. The three bright spores are still dormant. GEORGE KORZA

EDITOR’S CHOICE IN MICROBIOLOGY

The Paper
G. Korza et al., “Changes in Bacillus spore small molecules, rRNA, germination and outgrowth after extended sub-lethal exposure to various temperatures: Evidence that protein synthesis is not essential for spore germination,” J Bacteriol, doi:10.1128/JB.00583-16, 2016.

The History
For decades, scientists considered protein synthesis nonessential for the transition of dormant bacterial spores into active cells—a process known as germination. But a series of experiments from Sigal Ben-Yehuda’s lab at the Hebrew University of Jerusalem in recent years suggested otherwise. Spores with disrupted translation didn’t germinate, the group found, and with tagged amino acids, “we could even identify proteins synthesized during this period [of germination],” Ben-Yehuda says.

Second Test
After seeing Ben-Yehuda’s results, Peter Setlow of UConn Health in Farmington, Connecticut, wondered if he would find the same failure to germinate if he incubated the spores at high temperatures, which would degrade their ribosomes. So his team warmed up spores of Bacillus bacteria to 75–80 °C for nearly a day, thereby wiping out ribosomal RNA beyond the limits of detection.

Germination
Despite the spores’ lack of translational machinery, “they could still germinate,” Setlow says. “There were very slight effects.” Setlow suspects all the proteins necessary for germination are made in advance of dormancy, obviating the need for protein synthesis. “All the proteins are there and you just have to tickle it and say, ‘Go,’” he says.

Another Possibility
Ben-Yehuda says a lack of rRNA is not definitive evidence against protein synthesis occurring because rRNA can be made during germination. Her team showed previously that spores can make rRNA within a few minutes. Setlow says Ben-Yehuda’s data are convincing, and each team’s conclusions are consistent with the evidence. “That’s sort of where we sit,” he says. “We’ll see what happens in the future.”

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