Understanding the molecular mechanisms of gut commensal colonization, pathogen exclusion, and host-microbe interplay. (COMPLETED)


An Academy of Finland-funded research project (No. 277362) authored by Adjunct Prof. (Docent) Ingemar von Ossowski and awarded to Prof. (retired) Airi Palva.*


The menagerie of intestinal-friendly bacteria residing in the gut of humans and animals is a normal part of natural digestive health and well-being. For this, accumulating world-wide research suggests that these different bacterial genera and species, popularly termed as the gut microbiota, represent a beneficial storehouse of metabolic, protective, and structural processes. However, the properties and behavior of most individual bacteria remain obscure, particularly the manner in which some can permanently colonize the intestine. The funded research project has addressed this latter shortcoming by studying the gut colonization behavior of a paradigm commensal bacterium (Lactobacillus ruminis) and its ability to coexist as an indigenous member of the gut microbiota. As the ultimate goal, an attempt was made to correlate the contributive impact of L. ruminis ecological niche factors and their extracellular matrix (ECM) adhesion capacity to its distinctive gut indigenousness (or autochthony). Achieved project objectives included: (i) generating high-throughput genome data, thus laying groundwork for in silico comparative and predictive analyses, (ii) functional and structural characterization of novel niche factors and traits, and (iii) probing the host-cell interactions (e.g., by examining the propensity to localize in the gut, counteract invading intestinal pathogens, and trigger protective aspects of host immunity). Thus far, the tangible output from this research study is documented in three published peer-reviewed research articles, one published peer-reviewed review article, two published conference meeting abstracts, and two defended doctoral dissertations. Ten scientific journal publications ancillary to the research project, along with other manuscripts still pending, represent additional output. At a basic research level, it is our contention that this study of L. ruminis has advanced the biological understanding of one facet of the many interconnected ecological roles and functions played by intestinal bacteria and, in the wider context of the gut microbiota, has also provided valuable molecular insights into the concept of digestive well-being in humans and animals.

Prof. (retired) Airi Palva; project awardee
Adjunct Prof. (Docent) Ingemar von Ossowski; project author
Dr. Ravi Kant; bioinformatics specialist
Dr. Xia Yu; postdoctoral fellow
Dr. Silja Åvall-Jääskeläinen; university lecturer
Dr. Ulla Hynönen; postdoctoral fellow
Dr. Johanna Rintahaka; postdoctoral fellow
Dr. Agneta Lindholm; postdoctoral fellow
Annukka Jaatinen; MSc project student
Outi Lyytinen; laboratory assistant
Esa Pohjolainen; senior technician


(1) PUBLICATIONS (project-related)

von Ossowski I (2017) Novel molecular insights about lactobacillar sortase-dependent piliation. Int J Mol Sci 18(7):1551

Kant R, Palva A, von Ossowski I (2017) An in silico pan-genomic probe for the molecular traits behind Lactobacillus ruminis gut autochthony. PLoS ONE 12(4):e0175541

Yu X, Åvall-Jääskeläinen S, Koort J, Lindholm A, Rintahaka J, von Ossowski I, Palva A, Hynönen U (2017) A comparative characterization of different host-sourced Lactobacillus ruminis strains and their adhesive, inhibitory, and immunomodulating functions. Front Microbiol 8:657

Yu X, Åvall-Jääskeläinen S, Koort J, LindholmA, Rintahaka J, von Ossowski I, Palva A, Hynönen U (2017) Meeting abstract: A comparative characterization of different host-sourced Lactobacillus ruminis strains and their adhesive, inhibitory, and immunomodulating functions. Appli Micro Open Access 3(Suppl 2):32

Yu X, Rintahaka J, Jaatinen A, Hynönen U, Åvall-Jääskeläinen S, Lindholm A, von Ossowski I, Palva A (2016) Meeting abstract: Phenotypic characterization of a lactobacillar fimbrial operon through recombinant expression in Lactococcus lactis. J Clin Gastroenterol 50(Suppl 2):S209

Yu X, Jaatinen A, Rintahaka J, Hynönen U, Lyytinen O, Kant R, Åvall-Jääskeläinen S, von Ossowski I, Palva A (2015) Human gut-commensalic Lactobacillus ruminis ATCC 25644 displays sortase-assembled surface piliation: Phenotypic characterization of its fimbrial operon through in silico predictive analysis and recombinant expression in Lactococcus lactis. PLoS ONE 10(12):e0145718

(2) PUBLICATIONS (ancillary)

Megta AK, Palva A, von Ossowski I, Krishnan V (2019) SpaB, an atypically adhesive basal pilin from the lactobacillar SpaCBA pilus: crystallization and X-ray diffraction analysis. Acta Crystallogr F (accepted/in press, Nov 13)

Megta AK, Mishra AK, Palva A, von Ossowski I, Krishnan V (2019) Crystal structure of basal pilin SpaE reveals the molecular basis of its incorporation in the lactobacillar SpaFED pilus. ‎J Struct Biol 207:74-84

Chaurasia P, Pratap S, Palva A, von Ossowski I, Krishnan V (2018) Bent conformation of a backbone pilin N-terminal domain supports a three-stage pilus assembly mechanism. Commun Biol 1(1):94 *Journal editors’ pick of their favorite papers from the first year of publishing.

Mishra AK, Megta AK, Palva A, von Ossowski I, Krishnan V (2017) Crystallization and X-ray diffraction analysis of SpaE, a basal pilus protein from gut-adapted Lactobacillus rhamnosus GG. Acta Crystallogr F73:321-327

Chaurasia P, Pratap S, von Ossowski I, Palva A, Krishnan V (2016) New insights about pilus formation in gut-adapted Lactobacillus rhamnosus GG from the crystal structure of the SpaA backbone-pilin subunit. Sci Rep 6:28664

Kant A, von Ossowski I, Palva A, Krishnan V (2016) Crystallization and X-ray crystallographic analysis of the adhesive SpaC pilin subunit in the SpaCBA pilus of gut-adapted Lactobacillus rhamnosus GG. Protein Pept Lett 23:365-371

Chaurasia P. von Ossowski I, Palva A, Krishnan V (2015) Meeting abstract: X-ray diffraction analysis of two crystal forms of backbone pilin SpaA fragment from Lactobacillus rhamnosus GG. J Proteins Proteom 6(1):30

Chaurasia P, von Ossowski I, Palva A, Krishnan V (2015) Purification, crystallization, and preliminary X-ray diffraction analysis of SpaD, a backbone-pilin subunit encoded by the fimbrial spaFED operon in Lactobacillus rhamnosus GG. Acta Crystallogr. F71:103-106

Rintahaka J, Yu X, Kant R, Palva A, von Ossowski I (2014) Phenotypical analysis of the Lactobacillus rhamnosus GG fimbrial spaFED operon: Surface expression and functional characterization of recombinant SpaFED pili in Lactococcus lactis. PLoS ONE 9(11):e113922

Kant R, Rintahaka J, Yu X, Sigvart-Mattila P, Paulin L, Mecklin J-P, Saarela M, Palva A, von Ossowski I (2014) A comparative pan-genome perspective of niche-adaptable cell-surface protein phenotypes in Lactobacillus rhamnosus. PLoS ONE 9(7):e102762

(3) DEGREES (project-related)

PhD: Kant R (2018) Genomic insights about the Lactobacillus genus.(https://helda.helsinki.fi/handle/10138/236434; defended on June 26/2018)

PhD: Yu X (2018) Characterization of Lactobacillus pili and the niche-adaptation factors of intestinal Lactobacillus ruminis.(https://helda.helsinki.fi/handle/10138/230095; defended on Jan. 19/2018)

MSc: Jaatinen A (2012) Construction and characterization of recombinant Lactococcus lactis expressing surface-localized Lactobacillus ruminis pili.


von Ossowski I (2016) Appointed docent (adjunct professor) in molecular microbiology at the Faculty of Veterinary Medicine. (Nov 18/2016)

* A note of gratitude and appreciation is extended to the Academy of Finland for their decision to fund this research project.

Effective start/end date01/09/201431/08/2018