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Two sulphur-oxidizing, chemolithoautotrophic aerobes were isolated from the chemocline of an anchialine sinkhole located within the Weeki Wachee River of Florida. Gram-stain-negative cells of both strains were motile, chemotactic rods. Phylogenetic analysis of the 16S rRNA gene and predicted amino acid sequences of ribosomal proteins, average nucleotide identities, and alignment fractions suggest the strains HH1 T and HH3 T represent novel species belonging to the genus Thiomicrorhabdus . The genome G+C fraction of HH1 T is 47.8 mol% with a genome length of 2.61 Mb, whereas HH3 T has a G+C fraction of 52.4 mol% and 2.49 Mb genome length. Major fatty acids of the two strains included C 16 : 1 , C 18 : 1 and C 16 : 0 , with the addition of C 10:0 3-OH in HH1 T and C 12 : 0 in HH3 T . Chemolithoautotrophic growth of both strains was supported by elemental sulphur, sulphide, tetrathionate, and thiosulphate, and HH1 T was also able to use molecular hydrogen. Neither strain was capable of heterotrophic growth or use of nitrate as a terminal electron acceptor. Strain HH1 T grew from pH 6.5 to 8.5, with an optimum of pH 7.4, whereas strain HH3 T grew from pH 6 to 8 with an optimum of pH 7.5. Growth was observed between 15–35 °C with optima of 32.8 °C for HH1 T and 32 °C for HH3 T . HH1 T grew in media with [NaCl] 80–689 mM, with an optimum of 400 mM, while HH3 T grew at 80–517 mM, with an optimum of 80 mM. The name Thiomicrorhabdus heinhorstiae sp. nov. is proposed, and the type strain is HH1 T (=DSM 111584 T =ATCC TSD-240 T ). The name Thiomicrorhabdus cannonii sp. nov is proposed, and the type strain is HH3 T (=DSM 111593 T =ATCC TSD-241 T ).
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Adaptive evolution of a minimal organism with a synthetic genome
The bacterial strain JCVI-syn3.0 stands as the first example of a living organism with a minimized synthetic genome, derived from the Mycoplasma mycoides genome and chemically synthesized in vitro. Here, we report the experimental evolution of a syn3.0- derived strain. Ten independent replicates were evolved for several hundred generations, leading to growth rate improvements of > 15%. Endpoint strains possessed an average of 8 mutations composed of indels and SNPs, with a pronounced C/G- > A/T transversion bias. Multiple genes were repeated mutational targets across the independent lineages, including phase variable lipoprotein activation, 5 distinct; nonsynonymous substitutions in the same membrane transporter protein, and inactivation of an uncharacterized gene. Transcriptomic analysis revealed an overall tradeoff reflected in upregulated ribosomal proteins and downregulated DNA and RNA related proteins during adaptation. This work establishes the suitability of synthetic, minimal strains for laboratory evolution, providing a means to optimize strain growth characteristics and elucidate gene functionality.
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- PAR ID:
- 10481396
- Publisher / Repository:
- iScience
- Date Published:
- Journal Name:
- iScience
- Volume:
- 26
- Issue:
- 9
- ISSN:
- 2589-0042
- Page Range / eLocation ID:
- 107500
- Subject(s) / Keyword(s):
- Bioengineering Evolutionary biology Synthetic biology.
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.isci.2023.107500
