Infection by Sclerotium rolfsii will cause serious disease and
lead to significant economic losses in chili pepper. In this
study, the response of pepper during S. rolfsii infection was
explored by electron microscopy, physiological determination
and integrated proteome and metabolome analyses. Our results
showed that the stomata of pepper stems were important
portals for S. rolfsii infection. The plant cell morphology
was significantly changed at the time of the fungal hyphae just
contacting (T1) or surrounding (T2) the pepper. The chlorophyll,
carotenoid, and MDA contents and the activities of
POD, SOD, and CAT were markedly upregulated at T1 and
T2. Approximately 4129 proteins and 823 metabolites were
clearly identified in proteome and metabolome analyses, respectively.
A change in 396 proteins and 54 metabolites in
pepper stem tissues was observed at T1 compared with 438
proteins and 53 metabolites at T2. The proteins and metabolites
related to photosynthesis and antioxidant systems in
chloroplasts and mitochondria were disproportionally affected
by S. rolfsii infection, impacting carbohydrate and amino
acid metabolism. This study provided new insights into the
response mechanism in pepper stems during S. rolfsii infection,
which can guide future work on fungal disease resistance
breeding in pepper.
A polyphasic taxonomy approach was used to characterize
strain YBJ-36T, isolated from a freshwater lake in Taiwan.
Phylogenetic analyses, based on 16S rRNA gene sequences
and coding sequences of an up-to-date bacterial core gene
set (92 protein clusters), indicated that strain YBJ-36T formed
a phylogenetic lineage in the genus Mucilaginibacter. 16S
rRNA gene sequence similarity indicated that strain YBJ-36T
is closely related to species within the genus Mucilaginibacter
(93.8–97.8% sequence similarity) and is most similar to Mucilaginibacter
fluminis TTM-2T (97.8%), followed by Mucilaginibacter
roseus TTM-1T (97.2%). Microbiological analyses
demonstrated that strain YBJ-36T is Gram-negative, aerobic,
non-motile, rod-shaped, surrounded by a thick capsule, and
forms pink-colored colonies. Strain YBJ-36T grew between
20–40°C (optimal range, 35–37°C), pH 5.5–7.0 (optimal pH
of 6) and 0–2% NaCl (optimal concentration, 0.5%). The predominant
fatty acids of strain YBJ-36T are iso-C15:0 and summed
feature 3 (C16:1 ω7c and/or C16:1 ω6c), the major polar lipid
is phosphatidylethanolamine, the major polyamine is homospermidine,
and the major isoprenoid quinone is MK-7.
The draft genome is approximately 4.63 Mb in size with a
G+C content of 42.8 mol%. Strain YBJ-36T exhibited less than
35% DNA-DNA relatedness with Mucilaginibacter fluminis
TTM-2T and Mucilaginibacter roseus TTM-1T. Based on phenotypic
and genotypic properties and phylogenetic inference,
strain YBJ-36T should be classified in a novel species of the
genus Mucilaginibacter, for which the name Mucilaginibacter
limnophilus sp. nov. is proposed. The type strain is YBJ-36T
(= BCRC 81056T = KCTC 52811T = LMG 30058T).