Ammonia-oxidizing archaea and ammonia-oxidizing bacteria in six full-scale wastewater treatment bioreactors

In this study, dideoxy sequencing and 454 high-throughput sequencing were used to analyze diversities of the ammonia monooxygenase (amoA) genes and the 16S rRNA genes of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in six municipal wastewater treatment plants. The results showed that AOB amoA genes were quite diverse in different wastewater treatment plants while the 16S rRNA genes were relatively conserved. Based on the observed complexity of amoA and 16S rRNA genes, most of the AOB can be assigned to the Nitrosomonas genus, with Nitrosomonas ureae, Nitrosomonas oligotropha, Nitrosomonas marina, and Nitrosomonas aestuarii being the four most dominant species. From the sequences of the AOA amoA genes, most AOA observed in this study belong to the CGI.1b group, i.e., the soil lineage. The AOB amoA and 16S rRNA genes were quantified by quantitative PCR and 454 high-throughput pyrosequencing, respectively. Although the results from the two approaches show some disconcordance, they both indicated that the abundance of AOB in activated sludge was very low

Serotonin Augments Gut Pacemaker Activity via 5-HT3 Receptors

Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity. Muscle preparations with myenteric plexus were isolated from the murine ileum. Spatio-temporal measurements of intracellular Ca2+ and electric activities in ICC were performed by employing fluorescent Ca2+ imaging and microelectrode array (MEA) systems, respectively. Dihydropyridine (DHP) Ca2+ antagonists and tetrodotoxin (TTX) were applied to suppress smooth muscle and nerve activities, respectively. 5-HT significantly enhanced spontaneous Ca2+ oscillations that are considered to underlie electric pacemaker activity in ICC. LY-278584, a 5-HT3 receptor antagonist suppressed spontaneous Ca2+ activity in ICC, while 2-methylserotonin (2-Me-5-HT), a 5-HT3 receptor agonist, restored it. GR113808, a selective antagonist for 5-HT4, and O-methyl-5-HT (O-Me-5-HT), a non-selective 5-HT receptor agonist lacking affinity for 5-HT3 receptors, had little effect on ICC Ca2+ activity. In MEA measurements of ICC electric activity, 5-HT and 2-Me-5-HT caused excitatory effects. RT-PCR and immunostaining confirmed expression of 5-HT3 receptors in ICC. The results indicate that 5-HT augments ICC pacemaker activity via 5-HT3 receptors. ICC appear to be a promising target for treatment of functional motility disorders of the gut, for example, irritable bowel syndrome

Protein S-guanylation by the biological signal 8-nitroguanosine 3\u27,5\u27-cyclic monophosphate

The signaling pathway of nitric oxide (NO) depends mainly on guanosine 3′,5′-cyclic monophosphate (cGMP, 1). Here we report the formation and chemical biology of a nitrated derivative of cGMP, 8-nitroguanosine 3′,5′-cyclic monophosphate (8-nitro-cGMP, 2), in NO-mediated signal transduction. Immunocytochemistry demonstrated marked 8-nitro-cGMP production in various cultured cells in an NO-dependent manner. This finding was confirmed by HPLC plus electrochemical detection and tandem mass spectrometry. 8-Nitro-cGMP activated cGMP-dependent protein kinase and showed unique redox-active properties independent of cGMP activity. Formation of protein Cys-cGMP adducts by 8-nitro-cGMP was identified as a new post-translational modification, which we call protein S-guanylation. 8-Nitro-cGMP seems to regulate the redox-sensor signaling protein Keap1, via S-guanylation of the highly nucleophilic cysteine sulfhydryls of Keap1. This study reveals 8-nitro-cGMP to be a second messenger of NO and sheds light on new areas of the physiology and chemical biology of signal transduction by NO