Gastrointestinal Microbial Ecology of Weaned Piglets Fed Diets with Different Levels of Glyphosate.

Glyphosate possesses antimicrobial properties, and the present study investigated potential effects of feed glyphosate on piglet gastrointestinal microbial ecology. Weaned piglets were allocated to four diets (glyphosate contents [mg/kg feed]: 0 mg/kg control [CON; i.e., basal diet with no glyphosate added], 20 mg/kg as Glyphomax commercial herbicide [GM20], and 20 mg/kg [IPA20] and 200 mg/kg [IPA200] as glyphosate isopropylamine [IPA] salt). Piglets were sacrificed after 9 and 35 days of treatment, and stomach, small intestine, cecum, and colon digesta were analyzed for glyphosate, aminomethylphosphonic acid (AMPA), organic acids, pH, dry matter content, and microbiota composition. Digesta glyphosate contents reflected dietary levels (on day 35, 0.17, 16.2, 20.5, and 207.5 mg/kg colon digesta, respectively). Overall, we observed no significant glyphosate-associated effects on digesta pH, dry matter content, and-with few exceptions-organic acid levels. On day 9, only minor gut microbiota changes were observed. On day 35, we observed a significant glyphosate-associated decrease in species richness (CON, 462; IPA200, 417) and in the relative abundance of certain Bacteroidetes genera: CF231 (CON, 3.71%; IPA20, 2.33%; IPA200, 2.07%) and g_0.24 (CON, 3.69%; IPA20, 2.07%; IPA200, 1.75%) in cecum. No significant changes were observed at the phylum level. In the colon, we observed a significant glyphosate-associated increase in the relative abundance of Firmicutes (CON, 57.7%; IPA20, 69.4%; IPA200, 66.1%) and a decrease in Bacteroidetes (CON, 32.6%; IPA20, 23.5%). Significant changes were only observed for few genera, e.g., g_0.24 (CON, 7.12%; IPA20, 4.59%; IPA200, 4.00%). In conclusion, exposing weaned piglets to glyphosate-amended feed did not affect gastrointestinal microbial ecology to a degree that was considered actual dysbiosis, e.g., no potential pathogen bloom was observed. IMPORTANCE Glyphosate residues can be found in feed made from genetically modified glyphosate-resistant crops treated with glyphosate or from conventional crops, desiccated with glyphosate before harvest. If these residues affect the gut microbiota to an extent that is unfavorable to livestock health and productivity, the widespread use of glyphosate on feed crops may need to be reconsidered. Few in vivo studies have been conducted to investigate potential impact of glyphosate on the gut microbial ecology and derived health issues of animals, in particular livestock, when exposed to dietary glyphosate residues. The aim of the present study was therefore to investigate potential effects on the gastrointestinal microbial ecology of newly weaned piglets fed glyphosate-amended diets. Piglets did not develop actual gut dysbiosis when fed diets, containing a commercial herbicide formulation or a glyphosate salt at the maximum residue level, defined by the European Union for common feed crops, or at a 10-fold-higher level.

Impact of Dietary Sodium Butyrate and Salinomycin on Performance and Intestinal Microbiota in a Broiler Gut Leakage Model.

Unfavorable alterations of the commensal gut microbiota and dysbacteriosis is a major health problem in the poultry industry. Understanding how dietary intervention alters the microbial ecology of broiler chickens is important for prevention strategies. A trial was conducted with 672 Ross 308 day-old male broilers fed a basic diet (no additives, control) or the basic diet supplemented with 500 mg/kg encapsulated butyrate or 68 mg/kg salinomycin. Enteric challenge was induced by inclusion of 50 g/kg rye in a grower diet and oral gavage of a 10 times overdose of a vaccine against coccidiosis. Compared to control and butyrate-supplemented birds, salinomycin supplementation alleviated growth depression. Compared to butyrate and non-supplemented control, salinomycin increased potentially beneficial Ruminococcaceae and reduced potentially pathogenic Enterobacteriaceae and counts of Lactobacillus salivarius and Clostridium perfringens. Further, salinomycin supplementation was accompanied by a pH decrease and succinic acid increase in ceca, while coated butyrate (0.5 g/kg) showed no or limited effects. Salinomycin alleviated growth depression and maintained intestinal homeostasis in the challenged broilers, while butyrate in the tested concentration showed limited effects. Thus, further investigations are required to identify optimal dietary inclusion rates for butyrate used as alternative to ionophore coccidiostats in broiler production.

Halomonas aestuarii sp. nov., a moderately halophilic bacterium isolated from a tidal flat.

Strain Hb3T was isolated from a tidal flat in Jeollabuk-do Gunsan, Republic of Korea. Cells were Gram-stain-negative, oxidase- and catalase-positive, rod-shaped and motile. The strain grew optimally at 25-35 °C, at pH 6.0-6.5 and with 3.0-10.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Hb3T belonged to the genus Halomonas. Strain Hb3T was related most closely to Halomonas ventosae Al12T (98.6 % 16S rRNA gene sequence similarity), Halomonas denitrificans M29T (98.6 %) and Halomonas saccharevitans AJ275T (98.4 %). Moreover, multilocus sequence analysis using the gyrB, rpoD and secA genes supported the phylogenetic position of strain Hb3T. The genomic G+C content of strain Hb3T was 67.9 mol%. DNA-DNA hybridization values for strain Hb3T versus H. ventosae Al12T, H. denitrificans M29T and H. saccharevitans AJ275T were 38.0, 54.5 and 47.4 %, respectively. The major quinone was ubiquinone Q-9 and the major fatty acids were C18 : 1ω7c, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c), C16 : 0 and C19 : 0 cyclo ω8c. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, amino lipid, six unidentified phospholipids and an unidentified lipid comprised the polar lipid profile. On the basis of the data presented in this report, strain Hb3T represents a novel species of the genus Halomonas. The name Halomonas aestuarii sp. nov. is proposed for this novel species. The type strain is Hb3T (=KCTC 52253T=JCM 31415T).

Marinobacter salinus sp. nov., a moderately halophilic bacterium isolated from a tidal flat environment.

Two Gram-stain-negative, aerobic, motile, halophilic, rod-shaped bacteria, designated Hb8T and Hb20, were isolated from a tidal flat environment located on the South-West Korean peninsula. The isolates grew at 10-37 °C, at pH 5.0-9.0 and in NaCl concentrations of 0.5-15 % (w/v; optimum, 3.0-6.0 %). Sequence analysis of the 16S rRNA indicated that the isolates belong to the genus Marinobacter and are most closely related to Marinobacter sediminumR65T (98.3 %), followed by Marinobacter lipolyticus SM19T, Marinobacter salsuginis SD-14BT and Marinobacter similis A3d10T. The overall 16S rRNA gene sequence similarity with these species was 97.9 %, but Hb8T and Hb20 showed 100 % sequence similarity with each other. DNA-DNA relatedness values of H8T and Hb20 suggested that these isolates represent a single species, while DNA-DNA relatedness values of the two novel isolates with M. sediminum DSM 27079T and M. similis DSM 15400T were only 21.3 and 22.9 %, respectively. The major fatty acids present in strain Hb8T were identified as C16 : 0, C16 : 1ω9c, C18 : 1ω9c, C18 : 0 3-OH and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c). Ubiquinone-9 was the main respiratory quinone in both the novel strains. The polar lipids found to be present included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, four unidentified phospholipids and five unidentified lipids. The genomic DNA G+C content of Hb8T and Hb20 was 54.5 mol%. Polyphasic analysis indicated that the two isolates are representatives of a novel species of the genus Marinobacte, for which the name Marinobacter salinus sp. nov. is proposed. The type strain is Hb8T (=KCTC 52255T=JCM 31416T).

Detection and Diversity of the Nitrite Oxidoreductase Alpha Subunit (nxrA) Gene of Nitrospina in Marine Sediments.

Nitrite-oxidizing bacteria (NOB) are chemolithoautotrophs that catalyze the oxidation of nitrite to nitrate, which is the second step of aerobic nitrification. In marine ecosystems, Nitrospina is assumed to be a major contributor to nitrification. To date, two strains of Nitrospina have been isolated from marine environments. Despite their ecological relevance, their ecophysiology and environmental distribution are understudied owing to fastidious cultivation techniques and the lack of a sufficient functional gene marker. To estimate the abundance, diversity, and distribution of Nitrospina in various marine sediments, we used nxrA, which encodes the alpha subunit of nitrite oxidoreductase, as a functional and phylogenetic marker. We observed that Nitrospina diversity in polar sediments was significantly lower than that of non-polar samples. Moreover, nxrA-like sequences revealed an unexpected diversity of Nitrospina, with approximately 41,000 different sequences based on a 95% similarity cutoff from six marine sediments. We detected nxrA gene copy numbers of up to 3.57 × 104 per gram of marine sediment sample. The results of this study provide insight into the distribution and diversity of Nitrospina, which is fundamentally important for understanding their contribution to the nitrogen cycle in marine sediments.