1. Why is it relatively easy to obtain a finished map for bacterial genomes?
Bacterial genomes are typically small (generally under 10 Mb, with most around 4-5 Mb) and usually consist of a single circular chromosome. They feature a high coding density (typically over 80%) and relatively few repetitive sequences. Additionally, bacterial genes lack introns. These characteristics make them much easier to assemble into a complete map compared to complex plant or animal genomes.
2. What is the difference between a finished map and general genome sequencing?
Genome sequencing results are categorized by assembly quality into draft, improved, and finished maps.
Draft maps are fragmented with about 95% coverage.
Improved maps connect more scaffolds, achieving around 98% coverage.
Finished maps aim for a complete, gap-free genomic sequence, representing the highest precision in assembly.
3. Can a finished map guarantee zero gaps?
Generally, a zero-gap assembly (or ≤3 contigs) can be guaranteed if the following conditions are met:
(1) Genome size ≤ 6 Mb;
(2) No sample contamination (neither intra- nor interspecific);
(3) Total number of chromosomes and plasmids ≤ 4;
(4) Transposons or repetitive sequences account for ≤ 20%, with the longest repeat ≤ 20 kb;
(5) GC content is between 30% and 70%;
(6) DNA quality meets third-generation sequencing requirements (e.g., no degradation or impurities).
If these parameters are exceeded, a zero-gap assembly cannot be guaranteed, though optimization strategies will be applied to maximize assembly completeness.
4. Can pathogenic bacteria be processed for a finished map?
Finished maps can be generated for some pathogenic bacteria. However, strains with extremely high infectivity may be rejected due to biosafety restrictions. Please provide the Latin name of the bacterium so the sequencing provider can evaluate it and decide whether to accept the project.
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