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516 results on '"Richnow, Hans H."'

7. Bacterial and Archaeal Viruses of Himalayan Hot Springs at Manikaran Modulate Host Genomes

Author

Sharma, Anukriti, Schmidt, Matthias, Kiesel, Bärbel, Mahato, Nitish K, Cralle, Lauren, Singh, Yogendra, Richnow, Hans H, Gilbert, Jack A, Arnold, Wyatt, and Lal, Rup

Subjects
Microbiology, Biological Sciences, Human Genome, Genetics, Infectious Diseases, 2.2 Factors relating to the physical environment, Aetiology, Infection, archaeal viruses, bacteriophages, scanning-electron microscopy, helium-ion microscopy, Caudovirales, Environmental Science and Management, Soil Sciences, Medical microbiology
Abstract

Hot spring-associated viruses, particularly the archaeal viruses, remain under-examined compared to bacteriophages. Previous metagenomic studies of the Manikaran hot springs in India suggested an abundance of viral DNA, which prompted us to examine the virus-host (bacterial and archaeal) interactions in sediment and microbial mat samples collected from the thermal discharges. Here, we characterize the viruses (both bacterial and archaeal) from this Himalayan hot spring using both metagenomics assembly and electron microscopy. We utilized four shotgun samples from sediment (78-98°C) and two from microbial mats (50°C) to reconstruct 65 bacteriophage genomes (24-200 kb). We also identified 59 archaeal viruses that were notably abundant across the sediment samples. Whole-genome analyses of the reconstructed bacteriophage genomes revealed greater genomic conservation in sediments (65%) compared to microbial mats (49%). However, a minimal phage genome was still maintained across both sediment and microbial mats suggesting a common origin. To complement the metagenomic data, scanning-electron and helium-ion microscopy were used to reveal diverse morphotypes of Caudovirales and archaeal viruses. The genome level annotations provide further evidence for gene-level exchange between virus and host in these hot springs, and augments our knowledgebase for bacteriophages, archaeal viruses and Clustered Regularly Interspaced Short Palindromic Repeat cassettes, which provide a critical resource for studying viromes in extreme natural environments.

Published
2018

9. Methanogenic Hydrocarbon Degradation: Evidence from Field and Laboratory Studies

Author

Jiménez, Núria, Richnow, Hans H, Vogt, Carsten, Treude, Tina, and Krüger, Martin

Subjects
Microbiology, Biological Sciences, Industrial Biotechnology, Anaerobiosis, Bacteria, Anaerobic, Biodegradation, Environmental, Climate Change, Coal, Environmental Pollution, Fermentation, Hydrocarbons, Metabolic Networks and Pathways, Methane, Oil and Gas Fields, Oil, Methanogenesis, Methane production rate, Technology, Biotechnology, Industrial biotechnology
Abstract

Microbial transformation of hydrocarbons to methane is an environmentally relevant process taking place in a wide variety of electron acceptor-depleted habitats, from oil reservoirs and coal deposits to contaminated groundwater and deep sediments. Methanogenic hydrocarbon degradation is considered to be a major process in reservoir degradation and one of the main processes responsible for the formation of heavy oil deposits and oil sands. In the absence of external electron acceptors such as oxygen, nitrate, sulfate or Fe(III), fermentation and methanogenesis become the dominant microbial metabolisms. The major end product under these conditions is methane, and the only electron acceptor necessary to sustain the intermediate steps in this process is CO2, which is itself a net product of the overall reaction. We are summarizing the state of the art and recent advances in methanogenic hydrocarbon degradation research. Both the key microbial groups involved as well as metabolic pathways are described, and we discuss the novel insights into methanogenic hydrocarbon-degrading populations studied in laboratory as well as environmental systems enabled by novel cultivation-based and molecular approaches. Their possible implications on energy resources, bioremediation of contaminated sites, deep-biosphere research, and consequences for atmospheric composition and ultimately climate change are also addressed.

Published
2016

17. The fate of sulfonamide resistance genes and anthropogenic pollution marker intI1 after discharge of wastewater into a pristine river

Author

Haenelt, Sarah, Wang, Gangan, Kasmanas, Jonas C., Musat, Florin, Richnow, Hans H., Nunes da Rocha, Ulisses, Mueller, Jochen A., and Musat, Niculina

Subjects
Life sciences, biology, class 1 integron, river ecosystem, one health, ddc:570, sulfamethoxazole, intI1, sul1, sul2, sulfonamide resistance
Abstract

Introduction: Currently there are sparse regulations regarding the discharge of antibiotics from wastewater treatment plants (WWTP) into river systems, making surface waters a latent reservoir for antibiotics and antibiotic resistance genes (ARGs). To better understand factors that influence the fate of ARGs in the environment and to foster surveillance of antibiotic resistance spreading in such habitats, several indicator genes have been proposed, including the integrase gene intI1 and the sulfonamide resistance genes sul1 and sul2. Methods: Here we used quantitative PCR and long-read nanopore sequencing to monitor the abundance of these indicator genes and ARGs present as class 1 integron gene cassettes in a river system from pristine source to WWTP-impacted water. ARG abundance was compared with the dynamics of the microbial communities determined via 16S rRNA gene amplicon sequencing, conventional water parameters and the concentration of sulfamethoxazole (SMX), sulfamethazine (SMZ) and sulfadiazine (SDZ). Results: Our results show that WWTP effluent was the principal source of all three sulfonamides with highest concentrations for SMX (median 8.6 ng/l), and of the indicator genes sul1, sul2 and intI1 with median relative abundance to 16S rRNA gene of 0.55, 0.77 and 0.65%, respectively. Downstream from the WWTP, water quality improved constantly, including lower sulfonamide concentrations, decreasing abundances of sul1 and sul2 and lower numbers and diversity of ARGs in the class 1 integron. The riverine microbial community partially recovered after receiving WWTP effluent, which was consolidated by a microbiome recovery model. Surprisingly, the relative abundance of intI1 increased 3-fold over 13 km of the river stretch, suggesting an internal gene multiplication. Discussion: We found no evidence that low amounts of sulfonamides in the aquatic environment stimulate the maintenance or even spread of corresponding ARGs. Nevertheless, class 1 integrons carrying various ARGs were still present 13 km downstream from the WWTP. Therefore, limiting the release of ARG-harboring microorganisms may be more crucial for restricting the environmental spread of antimicrobial resistance than attenuating ng/L concentrations of antibiotics.

Published
2023
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30. Reductive debromination by sponge-associated anaerobic bacteria coupled to carbon isotope fractionation

Author

Richnow, Hans H., Lopez, Nora A., Horna-Gray, Isabel, Nijenhuis, Ivonne, Ahn, Youngbeom, and H��ggblom, Max M

Subjects
Anaerobic, Microbial reductive dehalogenation, Carbon isotope fractionation, Bromophenol
Abstract

Marine sponges contain diverse brominated compounds as secondary metabolites and the sponge habitat appears to enrich for a population of anaerobic dehalogenating bacteria. Hence, there is interest in understanding how these natural and anthropogenic compounds are degraded in the marine environment. Compound specific isotope analysis (CSIA) is a useful tool to monitor and to quantify the degradation and fate of aquatic pollutants. The objective of this study was to evaluate whether reductive dehalogenation of brominated phenols by sponge-associated bacteria, including Desulfoluna spongiiphila, can be monitored by CSIA. Debromination of 2,6-dibromophenol to phenol by sponge-associated cultures resulted in measurable stable carbon isotope fractionation. All sponge-associated cultures showed similar isotopic enrichment factors (��). The �� values for two independent sponge-derived dehalogenating cultures were ���3.1 �� 1.5���, and ���3.0 �� 0.3���, and that of sponge associated sediment cultures ���2.0 �� 0.3���. Thus, we demonstrate that reductive debromination of 2,6-dibromophenol resulted in measurable carbon isotope fractionation and that CSIA can be used to assess reductive debromination and to monitor and estimate in vivo dehalogenation in a sponge animal., [Display omitted], ���Compound specific isotope analysis (CSIA) was evaluated for monitoring reductive dehalogenation.���Reductive debromination of 2,6-dibromophenol to phenol results in carbon isotope fractionation.���CSIA can assess reductive debromination and estimate in vivo organohalide flux in a sponge animal.

Published
2022
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