Fossils of 160-Million-Year-Old Blue-Stained Bacteria Discovered in China

Fossilized blue-staining bacteria that inhabit coniferous wood, drawing the interest of insects. Xenoxylon Phyllocladoides from the Jurassic Tier Ojisian Formation in China extends the early fossil history of blue-stained bacteria by around 80 million years, reconstructing the evolutionary timeline of this fungal group and offering fresh perspectives on the evolution of ecological relationships with wood-boring insects.

Blue staining bacteria form a distinctive group of wood-inhabiting fungi that do not have the capacity to degrade lignocellulose but can cause significant discoloration, particularly in conifers.

Generally, these fungi are not fatal to their hosts, though they can hasten tree mortality when linked with wood-boring insects.

Recent molecular phylogenetic studies suggest that blue-stained bacteria may represent an ancient group of fungi that existed during the late Paleozoic or early Mesozoic eras.

However, the geological aspects of blue-staining bacteria remain largely unexplored.

“Until 2022, the earliest confirmed fossil evidence of blue-staining bacteria was identified from the Cretaceous period in South Africa, around 80 million years ago,” stated Dr. Ning Tian, a paleontologist at Shenyang Normal University.

Dr. Tian and colleagues uncovered well-preserved fossilized hyphae from a 160-million-year-old petrified forest of Xenoxylon Phyllocladoides from the Tier Ojisian Formation in Northeast China.

“Microscopy revealed darkly pigmented fossil hyphae, resembling the characteristics of modern blue-staining bacteria responsible for forest discoloration,” they noted.

“Notably, when penetrating woody cell walls, hyphae usually form a specialized structure known as permeation pegs.”

“As they invade the wood cell walls, the mycelium tends to be finer and can more easily navigate this robust barrier.”

“The discovery of these penetrating pegs allowed us to confirm that the fossilized bacteria we encountered belong to the blue-stained fungal group.”

“Unlike wood-decomposing fungi that break down wood cell walls through enzyme secretion, blue-staining bacteria lack the enzymatic ability for wood degradation.”

“Instead, their mycelium breaches the wood cell wall mechanically using these penetrating pegs.”

“This discovery of Jurassic blue-staining bacteria from China marks the second report of such fungi and adds to the early fossil record of this group worldwide, as recognized by Nanjing Institute of Geology and Paleontology.”

“It also sheds light on the ecological interactions between blue-staining bacteria, plants, and insects during the Jurassic period.”

The bark beetle subfamily Scolytinae is considered a major spore disperser for present-day blue stain fungi.

However, molecular and fossil data indicate that Scolytinae likely originated before the early Cretaceous period.

Given the current Jurassic age of the fossil fungi, it is proposed that the spore dispersing agent was not Scolytinae but another wood-boring insect prevalent during that time.

The findings are detailed in a paper published in the June 2025 issue of the journal National Science Review.

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Ning Tian et al. 2025. Jurassic blue staining bacteria provide new insights into early evolution and ecological interactions. National Science Review 12 (6): NWAF160; doi: 10.1093/nsr/nwaf160