Mucosa-associated Faecalibacterium prausnitzii phylotype richness is reduced in patients with inflammatory bowel disease.

Faecalibacterium prausnitzii depletion in intestinal diseases has been extensively reported, but little is known about intraspecies variability. This work aims to determine if subjects with gastrointestinal disease host mucosa-associated F. prausnitzii populations different from those hosted by healthy individuals. A new species-specific PCR-denaturing gradient gel electrophoresis (PCR-DGGE) method targeting the 16S rRNA gene was developed to fingerprint F. prausnitzii populations in biopsy specimens from 31 healthy control (H) subjects and 36 Crohn's disease (CD), 23 ulcerative colitis (UC), 6 irritable bowel syndrome (IBS), and 22 colorectal cancer (CRC) patients. The richness of F. prausnitzii subtypes was lower in inflammatory bowel disease (IBD) patients than in H subjects. The most prevalent operational taxonomic units (OTUs) consisted of four phylotypes (OTUs with a 99% 16S rRNA gene sequence similarity [OTU99]), which were shared by all groups of patients. Their distribution and the presence of some disease-specific F. prausnitzii phylotypes allowed us to differentiate the populations in IBD and CRC patients from that in H subjects. At the level of a minimum similarity of 97% (OTU97), two phylogroups accounted for 98% of the sequences. Phylogroup I was found in 87% of H subjects but in under 50% of IBD patients (P = 0.003). In contrast, phylogroup II was detected in >75% of IBD patients and in only 52% of H subjects (P = 0.005). This study reveals that even though the main members of the F. prausnitzii population are present in both H subjects and individuals with gut diseases, richness is reduced in the latter and an altered phylotype distribution exists between diseases. This approach may serve as a basis for addressing the suitability of F. prausnitzii phylotypes to be quantified as a putative biomarker of disease and depicting the importance of the loss of these subtypes in disease pathogenesis.

Characterization of the chlorosome antenna of the filamentous anoxygenic phototrophic bacterium Chloronema sp. strain UdG9001.

The absorption and fluorescence properties of chlorosomes of the filamentous anoxygenic phototrophic bacterium Chloronema sp. strain UdG9001 were analyzed. The chlorosome antenna of Chloronema consists of bacteriochlorophyll (BChl) d and BChl c together with gamma-carotene as the main carotenoid. HPLC analysis combined with APCI LC-MS/MS showed that the chlorosomal BChls comprise a highly diverse array of homologues that differ in both the degree of alkylation of the macrocycle at C-8 and/or C-12 and the alcohol moiety esterified to the propionic acid group at C-17. BChl c and BChl d from Chloronema were mainly esterified with geranylgeraniol (33% of the total), heptadecanol (24%), octadecenol (19%), octadecanol (14%), and hexadecenol (9%). Despite this pigment heterogeneity, fluorescence emission of the chlorosomes showed a single peak centered at 765 nm upon excitation at wavelengths ranging from 710 to 740 nm. This single emission, assigned to BChl c, indicates an energy transfer from BChl d to BChl c within the same chlorosome. Likewise, incubation of chlorosomes under reducing conditions caused a weak increase in fluorescence emission, which indicates a small redox-dependent fluorescence. Finally, protein analysis of Chloronema chlorosomes using SDS-PAGE and MALDI-TOF-MS revealed the presence of a chlorosomal polypeptide with a molecular mass of 5.7 kDa, resembling the CsmA protein found in Chloroflexus aurantiacus and Chlorobium tepidum chlorosomes. Several minor polypeptides were also detected but not identified. These results indicate that, compared with other members of filamentous anoxygenic phototrophic bacteria and green sulfur bacteria, Chloronema possesses an antenna system with novel features that may be of interest for further investigations.