Water-soluble humic like substances (HULIS) in smoke particles emitted from combustion of biomass materials and coal were characterized by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. The formulas identified were classified into four main groups: CHO, CHON, CHOS, and CHONS. The average H/C and O/C ratios are 1.13-1.33, 1.01-1.13, 1.26-1.48, 1.09-1.24 and 0.21-0.41, 0.27-0.45, 0.41-0.46, 0.44-0.61 for the CHO, CHON, CHOS, and CHONS groups, respectively. The CHO compound was the predominant component (43%-72%) of the smoke HULIS from biomass burning (BB) and coal combustion, followed by the CHON group for BB-smoke HULIS and the S-containing groups (i.e., CHOS and CHONS) for coal-smoke HULIS. These results indicate that the primary HULIS emitted from biomass burning contain a high abundance of CHON species, which appear to be made up mainly of oxidized nitrogen functional groups such as nitro compounds and/or organonitrates. The coal-smoke HULIS contained more compounds with relatively low molecular weight and high aromaticity index (AI). They were significantly enriched in S-containing compounds with high double bond equivalent (≥4), and O/S ratios suggest that they are most likely made up of aromatic organosulfates and nitrooxy organosulfates that are usually found in polluted atmospheres. These findings imply that the primary emissions from combustion of biomass and coal fuels are potential sources of water-soluble HULIS in an atmospheric matrix and that coal combustion is an especially important source of sulfate compounds.

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Our understanding of the ruminal epithelial tissue-associated bacterial (defined as epimural bacteria in this study) community is limited. In this study, we aimed to determine whether diet influences the diversity of the epimural bacterial community in the bovine rumen. Twenty-four beef heifers were randomly assigned to either a rapid grain adaptation (RGA) treatment (n ‫؍‬ 18) in which the heifers were allowed to adapt from a diet containing 97% hay to a diet containing 8% hay over 29 days or to the control group (n ‫؍‬ 6), which was fed 97% hay. Rumen papillae were collected when the heifers were fed 97%, 25%, and 8% hay diets. PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR analysis were used to characterize rumen epimural bacterial diversity and to estimate the total epimural bacterial population (copy numbers of the 16S rRNA gene). The epimural bacterial diversity from RGA heifers changed (P ‫؍‬ 0.01) in response to the rapid dietary transition, whereas it was not affected in control heifers. A total of 88 PCR-DGGE bands were detected, and 44 were identified from phyla including Firmicutes, Bacteroidetes, and Proteobacteria. The bacteria Treponema sp., Ruminobacter sp., and Lachnospiraceae sp. were detected only when heifers were fed 25% and 8% hay diets, suggesting the presence of these bacteria is the result of adaptation to the high-grain diets. In addition, the total estimated population of rumen epimural bacteria was positively correlated with molar proportions of acetate, isobutyrate, and isovalerate, suggesting that they may play a role in volatile fatty acid metabolism in the rumen.The ruminal bacteria digest complex and simple carbohydrates in the rumen and produce nutrients, such as volatile fatty acids (VFA), microbial protein, and vitamins, for the host. The rumen bacteria have been classified into three groups based upon their locations of colonization within the rumen: those associated with liquid, attached to solid particles, and attached to the ruminal epithelium (defined as epimural bacteria) (4). To date, most studies have focused on the bacteria attached to solid particles and associated with liquid (13,16,23,35,42). These studies have revealed that the bacterial diversity in ruminal contents is highly responsive to changes in diet, age, and antibiotic use, with the health status of the host, geographical location, and season further contributing to variation in diversity (42).While they account for only approximately 1 to 2% of the total bacterial population in the rumen (34), it has been suggested that epimural bacteria play essential roles in oxygen scavenging (6), urea hydrolysis (10, 47), and tissue recycling (25). As epimural bacteria are directly attached to the epithelial lining, they may also be involved in host-microbial interactions, and they may have a role in barrier function for rumen tissue, which is exposed to various fermented products. The epimural bacteria have been reported to be taxonomically distinct from those in the rumen fluid or ...