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- Autotrophy to Heterotrophy: Shift in Bacterial Functions During the Melt Season in Antarctic Cryoconite Holes.
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Aritri Sanyal, Runa Antony, Gautami Samui, Meloth Thamban
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J. Microbiol. 2024;62(8):591-609. Published online May 30, 2024
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DOI: https://doi.org/10.1007/s12275-024-00140-1
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Abstract
- Microbes residing in cryoconite holes (debris, water, and nutrient-rich ecosystems) on the glacier surface actively participate in carbon and nutrient cycling. Not much is known about how these communities and their functions change during the summer melt-season when intense ablation and runoff alter the influx and outflux of nutrients and microbes. Here, we use high-throughput-amplicon sequencing, predictive metabolic tools and Phenotype MicroArray techniques to track changes in bacterial communities and functions in cryoconite holes in a coastal Antarctic site and the surrounding fjord, during the summer season. The bacterial diversity in cryoconite hole meltwater was predominantly composed of heterotrophs (Proteobacteria) throughout the season. The associated functional potentials were related to heterotrophic-assimilatory and -dissimilatory pathways. Autotrophic Cyanobacterial lineages dominated the debris community at the beginning and end of summer, while heterotrophic Bacteroidota- and Proteobacteria-related phyla increased during the peak melt period. Predictive functional analyses based on taxonomy show a shift from predominantly phototrophy-related functions to heterotrophic assimilatory pathways as the melt-season progressed. This shift from autotrophic to heterotrophic communities within cryoconite holes can affect carbon drawdown and nutrient liberation from the glacier surface during the summer. In addition, the flushing out and export of cryoconite hole communities to the fjord could influence the biogeochemical dynamics of the fjord ecosystem.
- Comparison of Ganoderma boninense Isolate’s Aggressiveness Using Infected Oil Palm Seedlings
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Mei Lieng Lo , Tu Anh Vu Thanh , Frazer Midot , Sharon Yu Ling Lau , Wei Chee Wong , Hun Jiat Tung , Mui Sie Jee , Mei-Yee Chin , Lulie Melling
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J. Microbiol. 2023;61(4):449-459. Published online April 25, 2023
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DOI: https://doi.org/10.1007/s12275-023-00040-w
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Abstract
- Basal stem rot incidence caused by a white-rot fungus, Ganoderma boninense, is the major disease of oil palm in Southeast
Asia. The rate of disease transmission and host damage are affected by variations in pathogen aggressiveness. Several other
studies have used the disease severity index (DSI) to determine G. boninense aggressiveness levels while verifying disease
using a culture-based method, which might not provide accurate results or be feasible in all cases. To differentiate G.
boninense aggressiveness, we employed the DSI and vegetative growth measurement of infected oil palm seedlings. Disease
confirmation was performed through scanning electron microscopy and molecular identification of fungal DNA from both
infected tissue and fungi isolated from Ganoderma selective medium. Two-month-old oil palm seedlings were artificially
inoculated with G. boninense isolates (2, 4A, 5A, 5B, and 7A) sampled from Miri (Lambir) and Mukah (Sungai Meris and
Sungai Liuk), Sarawak. The isolates were categorized into three groups: highly aggressive (4A and 5B), moderately aggressive
(5A and 7A), and less aggressive (2). Isolate 5B was identified as the most aggressive, and it was the only one to result
in seedling mortality. Out of the five vegetative growth parameters measured, only the bole size between treatments was not
affected. The integration of both conventional and molecular approaches in disease confirmation allows for precise detection.
- Description of Corynebacterium poyangense sp. nov., isolated from the feces of the greater white-fronted geese (Anser albifrons)
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Qian Liu , Guoying Fan , Kui Wu , Xiangning Bai , Xi Yang , Wentao Song , Shengen Chen , Yanwen Xiong , Haiying Chen
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J. Microbiol. 2022;60(7):668-677. Published online May 25, 2022
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DOI: https://doi.org/10.1007/s12275-022-2089-9
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Abstract
- Two novel Gram-positive, non-spore-forming, facultatively
anaerobic, non-motile, and short rods to coccoid strains were
isolated from the feces of the greater white-fronted geese
(Anser albifrons) at Poyang Lake. The 16S rRNA gene sequences
of strains 4H37-19T and 3HC-13 shared highest identity
to that of Corynebacterium uropygiale Iso10T (97.8%).
Phylogenetic and phylogenomic analyses indicated that strains
4H37-19T and 3HC-13 formed an independent clade within
genus Corynebacterium and clustered with Corynebacterium
uropygiale Iso10T. The average nucleotide identity and digital
DNA-DNA hybridization value between strains 4H37-19T and
3HC-13 and members within genus Corynebacterium were
all below 95% and 70%, respectively. The genomic G + C content
of strains 4H37-19T and 3HC-13 was 52.5%. Diphosphatidylglycerol
(DPG), phosphatidylglycerol (PG), phosphatidylinositol
(PI), phosphatidylcholine, and phosphatidyl inositol
mannosides (PIM) were the major polar lipids, with
C18:1ω9c, C16:0, and C18:0 as the major fatty acids, and MK-8
(H4), MK-8(H2), and MK-9(H2) as the predominant respiratory
quinones. The major whole cell sugar was arabinose,
and the cell wall included mycolic acids. The cell wall peptidoglycan
contained meso-diaminopimelic acid (meso-DAP).
The polyphasic taxonomic data shows that these two strains
represent a novel species of the genus Corynebacterium, for
which the name Corynebacterium poyangense sp. nov. is
proposed. The type strain of Corynebacterium poyangense
is 4H37-19T (=GDMCC 1.1738T = KACC 21671T).
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