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Arginine Catabolism and Polyamine Biosynthesis Pathway Disparities Within Francisella tularensis Subpopulations
Ist Teil von
Frontiers in microbiology, 2022-06, Vol.13, p.890856-890856
Ort / Verlag
Frontiers Media S.A
Erscheinungsjahr
2022
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
Francisella tularensis
is a highly infectious zoonotic pathogen with as few as 10 organisms causing tularemia, a disease that is fatal if untreated. Although
F. tularensis
subspecies
tularensis
(type A) and subspecies
holarctica
(type B) share over 99.5% average nucleotide identity, notable differences exist in genomic organization and pathogenicity. The type A clade has been further divided into subtypes A.I and A.II, with A.I strains being recognized as some of the most virulent bacterial pathogens known. In this study, we report on major disparities that exist between the
F. tularensis
subpopulations in arginine catabolism and subsequent polyamine biosynthesis. The genes involved in these pathways include the
speHEA
and
aguAB
operons, along with
metK
. In the hypervirulent
F. tularensis
A.I clade, such as the A.I prototype strain SCHU S4, these genes were found to be intact and highly transcribed. In contrast, both subtype A.II and type B strains have a truncated
speA
gene, while the type B clade also has a disrupted
aguA
and truncated
aguB
. Ablation of the chromosomal
speE
gene that encodes a spermidine synthase reduced subtype A.I SCHU S4 growth rate, whereas the growth rate of type B LVS was enhanced. These results demonstrate that spermine synthase SpeE promotes faster replication in the
F. tularensis
A.I clade, whereas type B strains do not rely on this enzyme for
in vitro
fitness. Our ongoing studies on amino acid and polyamine flux within hypervirulent A.I strains should provide a better understanding of the factors that contribute to
F. tularensis
pathogenicity.