Mock microbial community meta-analysis using different trimming of amplicon read lengths.

Trimming of sequencing reads is a pre-processing step that aims to discard sequence segments such as primers, adapters and low quality nucleotides that will interfere with clustering and classification steps. We evaluated the impact of trimming length of paired-end 16S and 18S rRNA amplicon reads on the ability to reconstruct the taxonomic composition and relative abundances of communities with a known composition in both even and uneven proportions. We found that maximizing read retention maximizes recall but reduces precision by increasing false positives. The presence of expected taxa was accurately predicted across broad trim length ranges but recovering original relative proportions remains a difficult challenge. We show that parameters that maximize taxonomic recovery do not simultaneously maximize relative abundance accuracy. Trim length represents one of several experimental parameters that have non-uniform impact across microbial clades, making it a difficult parameter to optimize. This study offers insights, guidelines, and helps researchers assess the significance of their decisions when trimming raw reads in a microbiome analysis based on overlapping or non-overlapping paired-end amplicons.

Seasonal bacterial niche structures and chemolithoautotrophic ecotypes in a North Atlantic fjord.

Quantifying the temporal change of bacterial communities is essential to understanding how both natural and anthropogenic pressures impact the functions of coastal marine ecosystems. Here we use weekly microbial DNA sampling across four years to show that bacterial phyla have distinct seasonal niches, with a richness peak in winter (i.e., an inverse relationship with daylength). Our results suggest that seasonal fluctuations, rather than the kinetic energy or resource hypotheses, dominated the pattern of bacterial diversity. These findings supplement those from global analyses which lack temporal replication and present few data from winter months in polar and temperate regions. Centered log-ratio transformed data provided new insights into the seasonal niche partitioning of conditionally rare phyla, such as Modulibacteria, Verrucomicrobiota, Synergistota, Deinococcota, and Fermentibacterota. These patterns could not be identified using the standard practice of ASV generation followed by rarefaction. Our study provides evidence that five globally relevant ecotypes of chemolithoautotrophic bacteria from the SUP05 lineage comprise a significant functional group with varying seasonal dominance patterns in the Bedford Basin.

Incidence and patterns of mandibular fractures during a 5-year period in a London teaching hospital.

We retrospectively evaluated mandibular fractures in patients who presented to a London teaching hospital between June 2005 and May 2010. A total of 1261 patients sustained 1994 mandibular fractures (mean 1.6, range 1-5). The incidence of mandibular fracture was higher in male patients (87%) than in females (13%) (male:female ratio 6.6:1), and the peak incidence was during the third decade for both genders. The most common site of fracture was the angle (30%), followed by the parasymphysis (27%), and condyle (27%). Overall, interpersonal violence was the most common cause (72%) followed by falls (18%). In male patients, the most common cause was interpersonal violence (77%); in females it was a fall (46%). The anatomical sites of fracture reflected their cause. Interpersonal violence typically resulted in fractures of the angle (36%) while road traffic accidents and falls resulted in condylar fractures (28% and 53%, respectively). A total of 66 (5%) patients sustained other maxillofacial fractures and 37 (3%) presented with non-maxillofacial fractures. Our findings are consistent with trends reported in other urban centres.