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Common Floral Bacteria Can Induce Pollen Germination

The Bacteria Can Double Amount of Protein Released from Pollen

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close up of Acinebactor, a bacteria common in flowers, interacting with pollen grains that are germinating and bursting
This image shows what pollen looks like with Acinetobacter, a genus of bacteria common in flowers. Many of the pollen grains are germinating and bursting. (Shawn Christensen, 嘿嘿视频)

Certain species of floral bacteria can enhance pollen germination, according to published today from the University of California, Davis, in the journal Current Biology.

鈥淭his is the first paper documenting stimulation of pollen germination by non-plants,鈥 said first author Shawn Christensen, a doctoral candidate in associate professor in the Department of Entomology and Nematology. 鈥淣ectar-dwelling Acinetobacter bacteria stimulate protein release by inducing pollen to germinate and burst, benefiting Acinetobacter.鈥

Black and white image of doctoral student collecting poppies from 嘿嘿视频 Arboretum
Shawn Christensen, a microbiologist and doctoral candidate at 嘿嘿视频, collects poppies from the 嘿嘿视频 Arboretum. A tattoo of a pollen grain adorns his arm. (Benjamin Van Dolemen)

Acinetobacter is a genus of bacteria very common in flowers. They are usually among the most abundant bacteria in nectar and are often found on other floral tissues, including pollen and stigmas.

The authors collected California poppies from the 嘿嘿视频 Arboretum and Public Garden, and Acinetobacter primarily from nearby Stebbins Cold Canyon Reserve, which is part of the UC Natural Reserve System.

鈥淒espite the essential nutritional role of pollen for bees and other pollinators, we still know very little about how pollen is digested by anything,鈥 Christensen said. 鈥淲e found out that certain bacteria in flowers, Acinetobacter, can send a chemical signal to pollen that hijacks its systems and tells it to open the door from the inside 鈥 releasing protein and nutrients for the bacteria.鈥

Christensen said the bacteria can double the amount of protein released from pollen. That makes it important for bacterial growth, but it could also be exploited by bees or other pollen consumers to get more nutrition from their food.

The question of how organisms actually eat pollen has been a long-standing one. Pollen is well-protected by layers of resistant biopolymers, and it's unclear how pollen-eaters get through those protective layers.

鈥淭he bacteria have found what looks like a fairly unique and very effective way to get nutrients, which are otherwise scarce in a flower environment,鈥 said Vannette, a 嘿嘿视频 Hellman Fellow. 鈥淚t's a very neat biological trick. This finding opens the door for a lot of exciting new research: How do the bacteria do it? Given that Acinetobacter is often found on pollinators, do pollinators benefit from this? Could bacterial action on pollen make it more, or less, beneficial to pollen-eaters? And what about plants? Could the bacteria be reducing pollination by causing pollen to germinate before fertilization? We aim to investigate many of these possibilities in future work.鈥

Additional co-authors include Ivan Munkres of 嘿嘿视频.

The research was funded by the National Science Foundation, Davis Botanical Society, and 嘿嘿视频 Microbiology Graduate Group Diversity Equity and Inclusion Award.

Media Resources

  • Shawn Christensen, 嘿嘿视频 Department of Entomology and Nematology, smchristensen@ucdavis.edu
  • Rachel Vannette, 嘿嘿视频 Department of Entomology and Nematology, rlvannette@ucdavis.edu
  • Kathy Keatley Garvey, Communications, 嘿嘿视频 Department of Entomology and Nematology, kegarvey@ucdavis.edu 

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