“Expanding the Lactococcal Cell Wall Polysaccharide Paradigm: Novel Structures and Metabolic Pathways in the Emerging Dairy Species <i>Pseudolactococcus laudensis</i> and <i>Pseudolactococcus raffinolactis</i> ”
Bibliographic record
Abstract
Cell surface-associated polysaccharides, including cell wall polysaccharides (CWPSs), capsular polysaccharides (CPSs), and exopolysaccharides (EPSs), play vital roles in bacterial interactions with their environment, influencing critical aspects of dairy fermentations, such as phage-host dynamics. Pseudolactococcus laudensis and Pseudolactococcus raffinolactis (formerly Lactococcus laudensis and Lactococcus raffinolactis) are emerging dairy-associated species whose CWPSs remain uncharacterized. This study analyzed the complete genomes of 21 P. laudensis and seven P. raffinolactis strains to investigate the genetic diversity underlying CWPS and EPS production. Eight novel cwps genotypes (E-L) were identified, significantly expanding the known diversity within the dairy-associated (pseudo)lactococci. Notably, E and G genotypes diverge from the classical rhamnan-PSP organization, suggesting a CWPS biosynthesis pathway distinct from the dual-chain assembly found in previously studied Lactococcus. Additionally, eps loci were identified in 25 of the 28 strains, uncovering 11 distinct genotypes (I-XI) with evidence of horizontal gene transfer. Their integration into chromosomal genomic islands highlights their mobility and potential role in evolutionary adaptation. Chemical analysis revealed unprecedented CWPS structures. P. laudensis DSM 28961 (type E) presented a 6-deoxy-α-l-talan polysaccharide and a β-(1,4)-galactan, marking the first instance of d-talose replacing rhamnose and the first homopolysaccharide in (pseudo)lactococcal CWPS, respectively. These were structurally independent, confirming a novel CWPS organization and biosynthetic pathway. Conversely, P. raffinolactis DSM 20443 (type I) exhibited a typical rhamnan-PSP structure, composed of a variably glycosylated rhamnan and a glucose-lactose hexapolysaccharide, respectively. This study provides the first resolved CWPS structures for the Pseudolactococcus genus, expanding the understanding of polysaccharide biosynthesis in Lactic Acid Bacteria.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".