New morphological aspects of cephalodium formation in the lichenLobaria pulmonaria(Lecanorales, Ascomycota)

Abstract

Cephalodia were investigated on young and mature thalli of Lobaria pulmonaria. Cephalodia originate from contact between hyphae and cyanobacteria on the upper or lower cortex or, less frequently, in the apical zone. Young thalli were found to associate with cyanobacteria even in the anchoring zone. Cephalodia formed on the young thalli or the anchoring hyphae share the same phenotypic characteristics. In spite of being composed of paraplectenchymatous hyphae, the cortex of mature thalli preserves a considerable plasticity, enabling the formation of cephalodia. The cyanobacterial incorporation process begins with cortical hyphae growing out towards adjacent cyanobacterial colonies, enveloping them and incorporating them into the thallus. The incorporation process is the same on the upper and the lower cortex. Early stages of cephalodia are usually found in young lobes, whereas in the older parts of the thallus only mature cephalodia are found.

Exploring functional contexts of symbiotic sustain within lichen-associated bacteria by comparative omics

“…Bacterial communities primarily colonize the (hydrophilic) lichen surfaces, yet this pattern is strikingly different from the internalized symbionts in lichens, such as the green algae (D. reticulata in L. pulmonaria), which primarily contribute to the provision of photosynthetically produced carbohydrates. The greenalgal strain is massively enriched within the fungal structures, while cyanobacterial Nostoc strains are acquired from the surfaces of L. pulmonaria recurrently during the life-time of the thallus to form internal organs devoted to nitrogen fixation in lichens (Hyvärinen et al, 2002, Cornejo andScheidegger, 2013). Conversely, the external presence of other bacteria in the lichen symbiosis recalls the helper bacteria of mycorrhizal symbioses, which provide multiple functions to mutually support and stabilize the root symbioses, including exchange of carbohydrates and vitamin provision (Frey-Klett et al, 2007;Deveau et al, 2010).…”

“…The mycobiont of L. pulmonaria engulfs a green-algal photobiont (Dictyochloropsis reticulata; found in 90% of the lichen surface) and a minor cyanobacterial partner, Nostoc sp. (Cornejo and Scheidegger, 2013). Schneider et al (2011) provided an initial insight into the L. pulmonaria proteome and suggested Lobaria as an ideal model to study symbiotic processes.…”

Differential sharing and distinct co‐occurrence networks among spatially close bacterial microbiota of bark, mosses and lichens‬‬

“…For its function in nitrogen fixation of the lung lichen, Nostoc is of particular importance for the establishment of this lichen. Cornejo & Scheidegger () demonstrated that the cyanobacterial colonies are recurrently recruited from the environment and incorporated via uptake from the thallus surface into the growing thallus. Our results indicate that mosses may serve as rich reservoir of compatible Nostoc strains.…”

Microbial cargo: do bacteria on symbiotic propagules reinforce the microbiome of lichens?

“…The green‐algae Dictyochloropsis reticulata is found beneath more than 90% of the lichen surface and strains of cyanobacterium Nostoc are locally restricted to gall‐like colonies, in so‐called internal cephalodia (Myllys et al ., ). These Nostoc strains are generally captured from the surface to become gradually integrated into the lichen thallus, where they primarily contribute to the symbiotic system by nitrogen fixation (Jordan, ; Cornejo and Scheidegger, ).…”