Based on the BLAST results you provided, I can confirm that all 7 of the unplaced contigs (contig00020, contig00021, contig00022, contig00025, contig00026, contig00027, and contig00028) are indeed plasmid sequences.

Here is a breakdown of each contig, its likely plasmid type, and the supporting evidence from the BLAST hits:

1. contig00020

   • Verdict: Plasmid
   • Analysis: The top hits for this contig are to specific Acinetobacter baumannii plasmid records. The highest-scoring hit is to the plasmid from strain ATCC 19606 (Accession CP074586.1), titled “plasmid unnamed”. Other top hits include well-known plasmids like “pMAC”, “p2ATCC19606”, and “pAS645-3”.
   • Likely Identity: A multi-copy plasmid closely related to the pMAC/ATCC 19606 family of plasmids.

2. contig00021

   • Verdict: Plasmid
   • Analysis: The top hits for this contig are unequivocally plasmid sequences. The highest-scoring hit is to a specific plasmid, “p1ATCC19606” (Accession CP058290.1). Almost all of the top 100 hits are to various A. baumannii plasmids, including many named “p1…”, “p2…”, and “unnamed” plasmids.
   • Likely Identity: This contig matches the smaller, high-copy-number plasmid p1ATCC19606.

3. contig00022

   • Verdict: Plasmid
   • Analysis: This contig is the longest of the seven and its top hits are to chromosomes. However, this is a classic BLAST artifact. Since the chromosome contains the plasmid sequence integrated or as a repetitive element, a query with 100% identity will match the chromosome first due to its larger size and higher total score.
   • Evidence: To confirm it’s a plasmid, we look further down the hit list. For example, at rank 53, we see “Acinetobacter baumannii 1656-2, complete genome” (Accession CP001921.1). This record is actually a complete genome consisting of a chromosome AND 4 plasmids. Similarly, rank 74 is “Acinetobacter baumannii strain 2021CK-01407 plasmid unnamed1, complete sequence” (Accession CP104448.1).
   • Likely Identity: Despite the top chromosomal hits, the presence of strong plasmid hits confirms this is a plasmid sequence that is highly similar to sequences found on multiple chromosomes (likely due to integration or common repetitive elements).

4. contig00025

   • Verdict: Plasmid
   • Analysis: Similar to contig00022, the very top hits are to chromosomes, including the ATCC 19606 chromosome. Crucially, at rank 2, we see a hit to a “capsule biosynthesis gene locus” (Accession PV991066.1). While not a complete plasmid record, capsule loci are often located on plasmids or within genomic islands that can be plasmid-related.
   • Evidence: Deeper in the results (e.g., rank 32), we find direct matches to plasmids like “Acinetobacter lwoffii strain EK30A plasmid pALWEK1.12” (Accession CP080640.1). The wide variety of Acinetobacter species (lwoffii, variabilis, pseudolwoffii, etc.) in the hits suggests this sequence is a mobile genetic element, likely a plasmid or a transposon commonly found on plasmids, that is shared across the genus.
   • Likely Identity: A plasmid or plasmid-borne region (like a capsule locus) that is highly conserved across multiple Acinetobacter species.

5. contig00026

   • Verdict: Plasmid
   • Analysis: The top 97 hits for this contig are all to Acinetobacter baumannii chromosomes. At rank 98, however, we find “Acinetobacter sp. PVC-6A chromosome, complete genome” (Accession CP178379.1). The scientific name is “Acinetobacter sp. PVC-6A”, not A. baumannii. This indicates the sequence is present in a different species.
   • Likely Identity: This is almost certainly a plasmid or an integrated plasmid region. The sequence is 100% identical to a region in many A. baumannii chromosomes, but its presence in another Acinetobacter species (PVC-6A) strongly suggests it is a horizontally transferred element, such as a plasmid.

6. contig00027

   • Verdict: Plasmid
   • Analysis: This contig is clearly a plasmid. The top 7 hits are all to specific A. baumannii plasmid records, including “plasmid unnamed”, “p2ATCC19606”, “pMAC”, and “p1ATCC19606”. The subject lengths (e.g., 18598bp, 9540bp, 7655bp) are all typical plasmid sizes.
   • Likely Identity: A plasmid, likely from the same family as the pMAC/pATCC19606 plasmids found in strain ATCC 19606.

7. contig00028

   • Verdict: Plasmid
   • Analysis: Like contigs 22 and 25, the top hits are to A. baumannii chromosomes. However, at rank 40, there is a hit to “Acinetobacter sp. PVC-6A chromosome” (Accession CP178379.1), the same species identified in contig00026.
   • Likely Identity: A plasmid or plasmid-derived sequence that is shared between A. baumannii and other Acinetobacter species (like PVC-6A), indicating horizontal gene transfer.

Summary

Conclusion: All seven unplaced contigs are of plasmid origin. contig00020, contig00021, and contig00027 appear to be canonical plasmids matching known A. baumannii plasmid families. contig00022, contig00025, contig00026, and contig00028 appear to be plasmid sequences that are also found integrated into chromosomes or are highly promiscuous mobile elements shared across different Acinetobacter species.