Leptobacillium cavernicola Leplat, 2022

Leplat, Johann, Francois, Alexandre & Bousta, Faisl, 2022, Leptobacillium cavernicola, a newly discovered fungal species isolated from several Paleolithic-decorated caves in France, Phytotaxa 571 (2), pp. 186-196 : 190-193

Leptobacillium cavernicola Leplat , sp. nov. MB844042 ( Fig. 3 )

GenBank: OM622527 (ITS), OM628786 (LSU), OM628847 (SSU), OM677786 (RPB1), OM654326 (RPB2), OM654337 (TEF1-α)

Systematic position: Fungi, Dikarya, Ascomycota, Pezizomycotina, Sordariomycetes, Hypocreomycetidae, Hypocreales , Cordycipitaceae

Holotype:— FRANCE. Prignac-et-Marcamps , 45° 2’ 20” N, 0° 30’ 6” W, 22 October 2018. Isolated from surface sampling in the Pair-non-Pair cave, CBS 149113, preserved in a metabolically inactive state.

Etymology: The epithet cavernicola refers to the environment from which the strains of the species were mainly isolated, i.e. caves.

Colonies on MEA reached 12–24 mm diam. after 14 days at 25 °C, aerial mycelium can be scarce, velvety, white, slightly yellow exudate present in some strains. Reverse dark brown.

Colonies on PDA reached 14–20 mm diam. after 14 days at 25 °C, aerial mycelium can be scarce, velvety to floccose, white. Reverse usually dark brown. Yellow diffusible pigment present in some strains.

Phialides 5.1–27.2 x 1.2 –1.7 µm, mainly solitary, slender, tapering toward tip. Conidia 3.1–6.9 x 0.9 –1.5 µm, forming long, slender chains, narrowly cylindrical to slightly fusiform, some were slightly lemon-shaped, first-formed conidium were usually shorter, obovoid to pyriform with a rounded distal end.

Chlamydospore absent. Octahedral crystals not observed.

Other strains examined:— FRANCE. LRMH C212, LRMH C216, LRMH C302, LRMH C304, Cabrerets , 44° 30′ 27″ N, 1°38′ 40″ E, isolated from air samplings in Pech-Merle cave , LRMH C212 and LRMH C 216 in October 2016, LRMH C302 and LRMH C 304 in October 2018 ; LRMH C217, Prignac-et-Marcamps, 45° 2’ 20” N, 0° 30’ 6” W, October 2016, isolated from air sampling in Pair-non-Pair cave ; LRMH C313, LRMH C314, Les Eyzies-de-Taillac-Sireuil, 44° 56′ 37″ N, 1° 02′ 32″ E, October 2018, isolated from air samplings in Combarelles cave .

Notes: Leptobacillium cavernicola is distinguishable in the genus Leptobacillium by its slow growth rate on PDA at 25 °C, which is comparable to the rates recorded for L. leptobactrum var. leptobactrum and L. muralicola . However, caution should be applied when comparing with L. muralicola due to the differences in experimental protocol: Sun et al. (2019) studied the growth rate of this fungus at 20 °C over 10 days. The phialides produced by L. cavernicola seem shorter than those produced by L. leptobactrum var. leptobactrum and L. muralicola , and the difference between these three species is significantly supported by the phylogenetic data. The dark brown reverse of L. cavernicola on MEA and PDA media also seems to be characteristic of the species.

Figures

FIGURE 3. Leptobacillium cavernicola (Photographer: J. LEPLAT) a–b. Upper and reverse views of the culture on MEA (14 d at 25 °C). c–d. Upper and reverse views of the culture on PDA (14 d at 25 °C). e. Long chains of cylindrical to fusiform microconidia. The arrow indicates the typical first-formed conidium, which is shorter, obovoid to pyriform with a rounded distal end. f. Phialides, indicated by arrows. Scale bars: e–f = 10 µm.