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- Flavivirga spongiicola sp. nov. and Flavivirga abyssicola sp. nov., Isolated from Marine Environments
- Sung-Hyun Yang , Mi-Jeong Park , Hyun-Myung Oh , Yeong-Jun Park , Kae Kyoung Kwon
- J. Microbiol. 2024;62(1):11-19. Published online February 6, 2024
- DOI: https://doi.org/10.1007/s12275-023-00102-z
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Abstract
- Two novel Gram-stain-negative, strictly-aerobic, rod-shaped (1.2 ± 3.4 μm × 0.3 ± 0.7 μm), and non-motile marine bacterial species, designated MEBiC05379T and MEBiC07777T, were isolated from a marine sponge Pseudaxinella sp. in Gangneung City and deep-sea sediments of the Ulleung basin in the East Sea of Korea, respectively. The 16S rRNA gene sequence analysis revealed high levels of similarities between these strains and members of the genus Flavivirga (97.0–98.4% sequence identities). Both novel strains revealed as mesophilic, neutrophilic in pH and slightly halophilic. Similar to those of other Flavivirga members, the primary cellular fatty acids of both strains were iso-C15:0, iso-C15:1 G, iso-C15:03-OH, and iso-C17:0 3-OH, with MEBiC05379T and MEBiC07777T containing relatively higher proportions of C12: 0 and summed feature 3 ( C16:1ω7c and/or C16: 1ω6c). In both taxa, the major isoprenoid quinone was MK-6. The DNA G + C contents of MEBiC05379T and MEBiC07777T genomes were 32.62 and 32.46 mol%, respectively. Compared to other members of Flavivirga, both strains exhibited similar DNA G + C ratio and fatty acids pattern, yet enzyme expression and carbon sources utilization pattern were different. Genomes of the genus Flavivirga showed enzyme preferences to fucoidan and sulfated galactans. Considering the monophyly rule, AAI values delineate the genus Flavivirga from adjacent genera calculated to be 76.0–78.7%. Based on the phenotypic, genomic and biochemical data, strains for MEBiC05379T and MEBiC07777T thus represent two novel species in the genus Flavivirga, for which the names Flavivirga spongiicola sp. nov. ( MEBiC05379T [= KCTC 92527 T = JCM 16662 T]), and Flavivirga abyssicola sp. nov. ( MEBiC07777T [= KCTC 92563 T = JCM 36477 T]) are proposed.
- Deletion of lacD gene affected stress tolerance and virulence of Streptococcus suis serotype 2
- Xiaowu Jiang , Lexin Zhu , Dongbo Zhan
- J. Microbiol. 2022;60(9):948-959. Published online August 19, 2022
- DOI: https://doi.org/10.1007/s12275-022-2146-4
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Abstract
- Streptococcus suis type 2 (S. suis type 2, SS2), an infectious
pathogen which is zoonotic and can induce severely public
health concern. Our previous research identified a newly differential
secreted effector of tagatose-bisphosphate aldolase
(LacD) mediated by VirD4 factor within the putative type IV
secretion system of SS2, whereas the functional basis and roles
in virulence of LacD remain elusive. Here in this study, the
LacD was found enzymatic and can be activated to express
under oxidative stress. Gene mutant and its complemental
strain (ΔlacD and cΔlacD) were constructed to analyze the
phenotypes, virulence and transcriptomic profiles as compared
with the parental strain. The lacD gene deletion showed
no effect on growth capability and cells morphology of SS2.
However, reduced tolerance to oxidative and heat stress conditions,
increased antimicrobial susceptibility to ciprofloxacin
and kanamycin were found in ΔlacD strain. Further, the LacD
deficiency led to weakened invasion and attenuated virulence
since an easier phagocytosed and more prone to be cleared of
SS2 in macrophages were shown in ΔlacD mutant. Distinctive
transcriptional profiling in ΔlacD strain and typical downregulated
genes with significant mRNA changes including
alcohol dehydrogenase, GTPase, integrative and conjugative
elements, and iron ABC transporters which were mainly involved
in cell division, stress response, antimicrobial susceptibility
and virulence regulation, were examined and confirmed
by RNA sequencing and real time qPCR. In summary, the
results
demonstrated for the first time that LacD was a pluripotent protein mediated the metabolic, stress and virulent effect of SS2.
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