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Vikram Shivakumar

@vikramshivakumar.bsky.social
180 followers 142 following 41 posts

PhD Student @ JHU Langmead Lab

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Vikram Shivakumar @vikramshivakumar.bsky.social · 1h
Looks like it has mange! If you can call a local wildlife rescue, they could treat it, since it doesn’t look too far gone. Might’ve been relaxed because it was sick/tired 😞
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jakobheinz.bsky.social @jakobheinz.bsky.social · 01/10/2026
I’m excited to share our new preprint introducing HipHap, a tool for assigning long reads to haplotype-resolved diploid reference assemblies! With Max Marin, Matthew Meyerson, and @lh3lh3.bsky.social Preprint: www.biorxiv.org/content/10.6... 🧵 1/6
biorxiv.org
HipHap: Haplotype Assignment and Confidence Scoring for Diploid Reference Genomes
Diploid genome assemblies are now routinely available, but most read aligners were designed for haploid references, which have long been the gold standard. When reads are aligned to a diploid assembly...
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JHU Computer Science @jhucompsci.bsky.social · 30/09/2026
Congratulations to @benlangmead.bsky.social and @nathanielbrown.bsky.social on receiving a Best Paper Award for their work, “Bounding the Average Move Structure Query for Faster and Smaller RLBWT Permutations,” at the 24th Symposium on Experimental Algorithms!
cs.jhu.edu
Hopkins computer scientists win SEA Best Paper Award
The Symposium on Experimental Algorithms explores the role of experimentation and engineering techniques in the design and evaluation of algorithms and data structures.
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Ben Langmead @benlangmead.bsky.social · 30/09/2026
Have you been thinking of submitting an abstract to Genome Informatics UK this year? You still have time! The deadline is October 5. We'll see you there. coursesandconferences.wellcomeconnectingscience.org/event/genome...
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Human Pangenome Reference Consortium @humanpangenome.bsky.social · 24/09/2026
Shredtools is making it easier to explore regions across a pangenome by quickly finding matching genomic regions across hundreds of genomes. The tool can identify a gene region across 476 human genomes in approximately half a second.  Read more: www.biorxiv.org/content/10.6...
biorxiv.org
Navigating the pangenome coordinate system with Shredtools
Existing notions of pangenome coordinates rely on hard-to-compute multiple sequence alignments. On the other hand, pangenome-wide exact unique matches (multi-MUMs) can be computed efficiently, and rep...
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Human Pangenome Reference Consortium @humanpangenome.bsky.social · 26/08/2026
Pangenome coordinates can be complex... Shredtools offers a new approach using exact matches to query pangenome data efficiently. Its tools can extract syntenic regions across hundreds of genomes, making pangenome-scale exploration more accessible. pubmed.ncbi.nlm.nih.gov/42465356/
pubmed.ncbi.nlm.nih.gov
Navigating the pangenome coordinate system with Shredtools - PubMed
Existing notions of pangenome coordinates rely on hard-to-compute multiple sequence alignments. On the other hand, pangenome-wide exact unique matches (multi-MUMs) can be computed efficiently, and represent conserved stretches of columns in the underlying MSA. We introduce Shredtools, which uses mul …
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Mao-Jan Lin @maojanlin.bsky.social · 03/08/2026
1/ Excited to share our preprint ImpuT2T: a pangenome-based assembly patching tool ImpuT2T scaffolds draft human assemblies with a pangenome (HPRC2) and patches gaps by leveraging linkage disequilibrium and sequence identity between contigs and reference haplotypes Code: github.com/maojanlin/Im...
biorxiv.org
ImpuT2T: Pangenome-Based Patching for Human Genome Assemblies
With improvements in sequencing and assembly have come many high-quality telomere-to-telomere assemblies and reference pangenomes. However, the long-read sequencing recipes needed for high quality ass...
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Ben Langmead @benlangmead.bsky.social · 29/07/2026
📢 Genome Informatics 2026 (Hinxton UK + virtual, 2–4 Dec) is coming! Some confirmed speakers now listed: coursesandconferences.wellcomeconnectingscience.org/event/genome... Early-bird registration & bursary deadlines: 7 Sept. Abstract deadline: 5 Oct. Please submit your work & join us!
Wellcome Genome Campus aerial shot
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bioRxiv Bioinfo @biorxiv-bioinfo.bsky.social · 29/07/2026
ImpuT2T: Pangenome-Based Patching for Human Genome Assemblies www.biorxiv.org/content/10.64898/20…
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
Huge thanks to @benlangmead.bsky.social for his constant support and mentorship throughout the project. It is bittersweet seeing this work out, since it closes out the final chapter of my PhD. But I plan to continue working with MUMs in the UK (not that kind of mum though...)
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
10/ The Shredtools HPRC tool is a fully client-side site, fetching multi-MUMs hosted through the AWS Open Data Sponsorship. It enables querying any region from any assembly across HPRC to fetch syntenic regions, even visualizing synteny directly in the browser. Give it a go and send any feedback!
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
9/ We can also fetch multi-MUMs using a "bumbl.bi" remotely, opening up possibilities for integrating multi-MUM information into genome browsers. To show this, we pre-computed multi-MUMs across all HPRC assemblies (N=476) and built an interactive web app: vikshiv.github.io/shredtools
vikshiv.github.io
Shredtools HPRC
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
8/ Shredtools queries are efficient thanks to a new index of multi-MUMs. We store MUMs in a binary "bumbl" format, and build a "bumbl.bi" index, similar to a bai file for a bam file. This enables rapid, random access fetching of matches in any query region from any assembly in a collection.
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
7/ multi-MUMs are also efficient to compute. Existing methods can use pairwise alignments to project coordinates across a pangenome, and we show Mumemto multi-MUMs are an order of magnitude faster and more memory-efficient to compute than pairwise genome alignments.
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
6/ Shredtools extract depends on the coverage of multi-MUMs. Another method, enhance, finds additional matches between MUMs that serve as additional markers of the coordinate system, approaching a full multiple alignment. Figure: extract across the A. thaliana pangenome ("enhanced" MUMs in purple)
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
5/ are multi-MUMs useful as a coordinate system? We found that multi-MUMs are the ideal choice over unique k-mers, which have lower coverage. And often, the choice of k varies greatly with various parameters of the pangenome.
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
4/ Shredtools reports "bounds", the distance between the ouput region to the nearest flanking MUMs. Querying gene regions across HPRC2 assemblies, more than 80% of regions were immediately flanked by a multi-MUM, yielding exact coordinates across all 476 human assemblies!
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
3/ Shredtools uses collinear multi-MUMs from Mumemto as a "coordinate system" for the pangenome, without computing a multiple alignment or graph. The highlight feature is extract: given a local region in any assembly, using multi-MUMs, Shredtools fetches syntenic regions across the whole pangenome!
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
2/ ⭐ highlight of the release: we implemented shredtools for the HPRC human pangenome as a browser-based, client-side app to query and fetch syntenic regions across the pangenome. You can even visualize synteny right in the browser! Read on for how the method works.
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Vikram Shivakumar @vikramshivakumar.bsky.social · 15/07/2026
1/ Excited to share the newest tool in the pangenome MUMiverse: Shredtools! Shredtools enables a user to navigate the pangenome coordinate system with multi-MUMs. More in the thread🧵 Code: github.com/vikshiv/shredtools Interactive tool for querying HPRC assemblies: vikshiv.github.io/shredtools
biorxiv.org
Navigating the pangenome coordinate system with Shredtools
Existing notions of pangenome coordinates rely on hard-to-compute multiple sequence alignments. On the other hand, pangenome-wide exact unique matches (multi-MUMs) can be computed efficiently, and rep...
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Sina Majidian @sinamajidian.bsky.social · 09/07/2026
JOB ALERT! I'm hiring two postdocs in Computational Genomics to join our lab in beautiful Gothenburg, Sweden. Please share and repost! CGRLab.github.io/research/
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Ben Langmead @benlangmead.bsky.social · 22/06/2026
Movi 2 has appeared (as an advance article) in Bioinformatics 🧬 Faster, leaner pangenome queries — half the memory of Movi 1, ~30% faster. Paper: academic.oup.com/bioinformati... Code: github.com/mohsenzakeri/Movi (1/6)
academic.oup.com
Validate User
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KamilSJaron.bsky.social @kamilsjaron.bsky.social · 19/06/2026
Last chance to register for a Scalable genomics course this autumn! It will be a banger. With @katiejenike.bsky.social @richard-durbin.bsky.social @npmalfoy.bsky.social and @vikramshivakumar.bsky.social! coursesandconferences.wellcomeconnectingscience.org/event/scalab...
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Vikram Shivakumar @vikramshivakumar.bsky.social · 21/05/2026
I’ve learned so much over my PhD, but I’ll never forget how to dodge a blue shell while in first place
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Vikram Shivakumar @vikramshivakumar.bsky.social · 21/05/2026
Very bittersweet for me too. I’ll always be grateful for your mentorship and for the amazing lab and community I’ve been fortunate to grow alongside over the years. I’ll definitely miss Baltimore and the wonderful genomics community at Hopkins. Looking forward to the next chapter in Cambridge!
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Vikram Shivakumar @vikramshivakumar.bsky.social · 13/03/2026
Thank you! And thanks to all the wonderful people at JHU I’ve had the pleasure of working with during my PhD. And of course, to my advisor @benlangmead.bsky.social and my super supportive thesis committee members @aphillippy.bsky.social and @mikeschatz.bsky.social. Excited to 🇺🇸 -> 🇬🇧 soon!
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Matthew Nguyen @mnguyen667.bsky.social · 09/03/2026
1/ Excited to share my first first-author preprint from my PhD! We introduce Perseus, a lineage-aware confidence estimation framework for taxonomic classification in long-read metagenomics. Preprint: www.biorxiv.org/content/10.6... Code: github.com/matnguyen/Pe...
biorxiv.org
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Vikram Shivakumar @vikramshivakumar.bsky.social · 02/03/2026
I wish I had this a few months back while searching for a postdoc 😅
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Vikram Shivakumar @vikramshivakumar.bsky.social · 02/03/2026
Awesome! Thanks for sharing the code too!
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Vikram Shivakumar @vikramshivakumar.bsky.social · 02/03/2026
Does this take into account how many pubs the first author had at publication time or what they have currently, when applying the filter? This is a really nifty measure and tool!
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Dr. Jean Fan @jef.works · 02/03/2026
As an alternative to the h-index, I made the Mentorship Index (M-index) to proxy a scientist's contribution to mentoring junior scientists. Ex. M10-index = # last-author publications where the first author had < 10 pubs. Calculate yours: jef.works/Mentorship-I... Blog: jef.works/blog/2026/03... 🧵👇
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Adam Phillippy @aphillippy.bsky.social · 29/01/2026
New tool from @alexsweeten.bsky.social to find and classify all your satellites: "AniAnn's: alignment-free annotation of tandem repeat arrays using fast average nucleotide identity estimates" 📄 www.biorxiv.org/content/10.6... 📦 github.com/marbl/anianns
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Mitchell R. Vollger @mrvollger.bsky.social · 12/01/2026
I am hiring a staff bioinformatician for my new lab at the University of Utah! Please consider applying if you are on the hunt: employment.utah.edu/salt-lake-ci...
employment.utah.edu
Jobs | University of Utah
Founded in 1850, The University of Utah is the flagship institution of higher learning in Utah, and offers over 100 undergraduate and more than 90 graduate degree programs to over 30,000 students. Uni...
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Heng Li @lh3lh3.bsky.social · 14/01/2026
I am looking for a postdoc to develop high-performance algorithms in computational genomics. Email or DM me if interested. For more information, see hlilab.github.io/vacancies. RTs appreciated!
hlilab.github.io
HLi Lab - Vacancies
Openings
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Vikram Shivakumar @vikramshivakumar.bsky.social · 23/11/2025
(t)rust the process?
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Vikram Shivakumar @vikramshivakumar.bsky.social · 07/11/2025
Really excited to see our new work in scaling Mumemto to any size pangenome published in Genome Research this morning. And right on cue with the great opportunity to present this work at #GI2025 this week.
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Sina Majidian @sinamajidian.bsky.social · 06/11/2025
Nicole Brown gave a fantastic talk on Identifying introgressions across pangenomes with Panagram It uses k-mer conservation to annotate genomic variation across hundreds of genomes, followed by normalization of k-mer profiles to identify introgression events github.com/kjenike/pana... #GI2025
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Sina Majidian @sinamajidian.bsky.social · 06/11/2025
Fantastic talk by @vikramshivakumar.bsky.social Mumemto—Scalable multi-MUM finding for pangenomes Papers biorxiv.org/content/10.1101/2025.05.20.654611 & doi.org/10.1186/s13059-025-03644-0 Code: github.com/vikshiv/mume... Very efficient pangenome visualization tool, revealing synteny and variations!
Figure 1: (A) Anchor-based merging requires a common sequence (red) present in each partition. Multi-MUMs are merged by identifying overlaps between partition-specific matches in the anchor coordinate space, and a uniqueness threshold determines if a MUM is still unique in each partition after truncation. (B) String-based merging enables compu- tation of multi-MUMs between partitions without a common sequence. An example tree (left) is shown, highlighting the use case where partial multi-MUMs specific to internal nodes (starred) can be computed by merging subclade-based partitions up a tree. (right) MUM overlaps are computed by running Mumemto on the MUM sequences, and the uniqueness threshold array ensures overlaps remain unique across the merged dataset. (C) An example Burrows-Wheeler Transform (BWT), matrix (BWM), and Longest Com- mon Prefix (LCP) array, with sequence IDs for each suffix shown (ID). A non-maximal unique match (UM) is shown, and the uniqueness threshold for this match is found us- ing the flanking LCP values. (D) A partial multi-MUM (in blue) is found in all-but-one sequence (excluded in red). Using two anchor sequences (red and orange), all-but-one partial MUMs can be computed using an augmented anchor-based merging method (sec- tion 2.6).
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Vikram Shivakumar @vikramshivakumar.bsky.social · 04/11/2025
Looking forward to lots of great talks from JHU folks at CSHL this week!
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Vikram Shivakumar @vikramshivakumar.bsky.social · 03/11/2025
Now this, undergrads, is how you cold email a professor.
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Adam Phillippy @aphillippy.bsky.social · 10/10/2025
If that’s not enough, we threw in a complete, T2T giraffe genome! Giraffe genomes are pretty cool. Almost all of their chromosomes are Robertsonian fusions of the typically telocentric ruminant chromosomes. 🐄 vs. 🦒...
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Adam Phillippy @aphillippy.bsky.social · 10/10/2025
Last week we were in the Washington Post for our characterization of Robertsonian chromosomes. This week we are entering our 10th day of being shut down and all of our research is on hold. To help me feel not-so-bad, here is a thread of some studies we released right before the shutdown 🧵 [1/n]...
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Sina Majidian @sinamajidian.bsky.social · 21/09/2025
Excited to share our EvANI benchmarking workflow, published in Briefings in Bioinformatics doi.org/10.1093/bib/... Computing average nucleotide identity (ANI) is neither conceptually nor computationally trivial. Its definition has evolved over years, with different meanings and assumptions (1/5)
Figure 1(A) ANI quantifies the similarity between two genomes. ANI can be defined as the number of aligned positions where the two aligned bases are identical, divided by the total number of aligned bases. Historically, ANI was calculated using a single gene family for multiple sequence alignment. Another approach finds orthologous genes between two genomes and reports the average similarity between their CDSs. This method was later extended to whole-genome alignment by identifying local alignments and excluding supplementary alignments with lower similarity. (B) Different ANI tools employ various approaches in calculating ANI values. ANIm, OrthoANI, and FastANI use aligners to identify homologous regions, whereas Mash uses k-mer hashing to estimate similarities. Only alignments with higher similarity represented by green arrows are included in ANI calculations, while red arrows, corresponding to paralogs, are excluded. (C) The proposed benchmarking method evaluates the performance of different tools using both real and simulated data. It assumes that more distantly related species on the phylogenetic tree should have lower ANI similarities. This is measured by calculating the statistics of Spearman rank correlation. We expect a negative correlation between ANI and the tree distance (scatter plot on the right).
https://academic.oup.com/bib/article/doi/10.1093/bib/bbaf267/8160681
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Vikram Shivakumar @vikramshivakumar.bsky.social · 22/08/2025
10/10 tool name 👌
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Sina Majidian @sinamajidian.bsky.social · 20/08/2025
Great talk by Vikram @vikramshivakumar.bsky.social on studying pangenomes and synteny visualization in #WABI25 Github: github.com/vikshiv/mume... First paper: genomebiology.biomedcentral.com/articles/10.... Second: www.biorxiv.org/content/10.1... #WABI2025
Anchor-based merging requires a common sequence (red) present in each partition. Multi-MUMs are merged by identifying overlaps between partition-specific matches in the anchor coordinate space, and a uniqueness threshold determines if a MUM is still unique in each partition after truncation. (B) String-based merging enables computation of multi-MUMs between partitions without a common sequence. An example tree (left) is shown, highlighting the use case where partial multi-MUMs specific to internal nodes (starred) can be computed by merging subclade- based partitions up a tree. (right) MUM overlaps are computed by running Mumemto on the MUM sequences, and the uniqueness threshold array ensures overlaps remain unique across the merged dataset. (C) An example Burrows-Wheeler Transform (BWT), matrix (BWM), and Longest Common Prefix (LCP) array, with sequence IDs for each suffix shown (ID). A non-maximal unique match (UM) is shown, and the uniqueness threshold for this match is found using the flanking LCP values. (D) A partial multi-MUM (in blue) is found in all-but-one sequence (excluded in red). Using two anchor sequences (red and orange), all-but-one partial MUMs can be computed using an augmented anchor-based merging method.
(A) Phylogeny of geographically diverse A. thaliana accessions (Lian et al. 2024), with broad geographical regions colored. Internal nodes are labeled with the coverage of partial multi-MUMs across the leaves of each node. Internal node partial MUMs are computed by merging subtree-based partitions progressively up the phylogeny. (B) Global multi-MUM synteny across the full dataset shown in blue (with inversions in green). Global MUMs are computed by merging all partitions together (representing the root node). Additionally, three geographically distinct subgroups are highlighted and partition-specific multi-MUMs (in purple, with inversions in pink) reveal local structural variation in centromeric regions.
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Rob Patro @robp.bsky.social · 20/08/2025
Vikram Shivakumar telling us about "Partitioned Multi-MUM finding for scalable pangenomics" #WABI25! So many kinds of matches!
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Liana Lareau @lianafaye.bsky.social · 07/08/2025
This preprint from Helen Sakharova is one of the coolest things to come out of my lab: “Protein language models reveal evolutionary constraints on synonymous codon choice.” Codon choice is a big puzzle in how information is encoded in genomes, and we have a new angle. www.biorxiv.org/content/10.1...
biorxiv.org
Protein language models reveal evolutionary constraints on synonymous codon choice
Evolution has shaped the genetic code, with subtle pressures leading to preferences for some synonymous codons over others. Codons are translated at different speeds by the ribosome, imposing constrai...
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Vikram Shivakumar @vikramshivakumar.bsky.social · 06/08/2025
Not saying I agree either way, but one pro for text-based file formats are less dependencies needed for viewing files
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Vikram Shivakumar @vikramshivakumar.bsky.social · 31/07/2025
This is so amazing, thank you!
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Petra Korlević @petrathepostdoc.bsky.social · 31/07/2025
#SciArt doodle of @vikramshivakumar.bsky.social's talk yesterday at the @sangerinstitute.bsky.social on MUMs* *maximal unique matches in pangenomes, now if you did that on sequenced moms you could do mummoms
comic doodle of Vikram Shivakumar in a sweater and checkered shirt on a pink gradient background, with various elements of the talk to the left: two old moms pointing at MUMs, below an explanation of what those are (large chunks of the same DNA sequence through the genome), at the bottom a few of the organisms worked on: a tomato, a potato, an arabidopsis weed.
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