Anaerobic organism

An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenated environment. Anaerobes may be unicellular (e.g. protozoans, bacteria) or multicellular. Most fungi are obligate aerobes, requiring oxygen to survive. However, some species, such as the Chytridiomycota that reside in the rumen of cattle, are obligate anaerobes; for these species, anaerobic respiration is used because oxygen will disrupt their metabolism or kill them. Deep waters of the ocean are a common anoxic environment. In his 14 June 1680 letter to The Royal Society, Antonie van Leeuwenhoek described an experiment he carried out by filling two identical glass tubes about halfway with crushed pepper powder, to which some clean rain water was added. Van Leeuwenhoek sealed one of the glass tubes using a flame and left the other glass tube open. Several days later, he discovered in the open glass tube 'a great many very little animalcules, of divers sort having its own particular motion.' Not expecting to see any life in the sealed glass tube, Van Leeuwenhoek saw to his surprise 'a kind of living animalcules that were round and bigger than the biggest sort that I have said were in the other water.' The conditions in the sealed tube had become quite anaerobic due to consumption of oxygen by aerobic microorganisms. In 1913, Martinus Beijerinck repeated Van Leeuwenhoek's experiment and identified Clostridium butyricum as a prominent anaerobic bacterium in the sealed pepper infusion tube liquid. Beijerinck commented: We thus come to the remarkable conclusion that, beyond doubt, Van Leeuwenhoek in his experiment with the fully closed tube had cultivated and seen genuine anaerobic bacteria, which would happen again only after 200 years, namely about 1862 by Pasteur. That Leeuwenhoek, one hundred years before the discovery of oxygen and the composition of air, was not aware of the meaning of his observations is understandable.

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related publications (3)

Related people (4)

Related units (1)

Related concepts (67)

Related courses (14)

Related lectures (103)

Related MOOCs (1)

ENV-202: Microbiology for engineers

"Microbiology for engineers" covers the main microbial processes that take place in the environment and in treatment systems. It presents elemental cycles that are catalyzed by microorganisms and that

ENG-436: Food biotechnology

The course will deliver basic knowledge on the principles of food fermentation and enzyme technology. The course will also present benefits that food biotechnology can bring in terms of Nutrition & He

BIO-378: Physiology lab I

Le TP de physiologie introduit les approches expérimentales du domaine biomédical, avec les montages de mesure, les capteurs, le conditionnement des signaux, l'acquisition et traitement de données. Le

Bacteria

Bacteria (bækˈtɪəriə; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere.

Anaerobic organism

Fermentation

Fermentation is a metabolic process that produces chemical changes in organic substances through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology.

Water quality and the biogeochemical engine

Learn about how the quality of water is a direct result of complex bio-geo-chemical interactions, and about how to use these processes to mitigate water quality issues.

Methylation of arsenic by single-species and soil-derived microbial cultures

Karen Elda Viacava Romo

Arsenic (As) is simultaneously a ubiquitous and a toxic element. Arsenic is subject to bio-transformations catalyzed by microorganisms constituting the As biogeochemical cycle. The primordial Earth was devoid of oxygen, exposing life to the highly mobile and toxic arsenite. This early contact with As is imprinted in the tree of life as arsenic resistance genes, e.g. arsenite efflux by transmembrane transporters. Arsenic bio-transformations includes As methylation catalyzed by the ArsM enzyme. ArsM attaches methyl groups to inorganic As, generating organic As in the trivalent (highly toxic species) and pentavalent (relatively innocuous species) forms. Worldwide concern about exposure to As has been raised due to the high As levels in groundwater in South-East Asia used for consumption and rice cultivation. Rice plants are grown under flooded conditions which are conducive to arsenite mobilization and uptake by roots, resulting in the presence of inorganic and methylated As in grains. Compared to inorganic As, methylarsenicals are more easily accumulated in rice grains and are implicated in rice plant disorders resulting in sterility. Methylated species are not synthesized by the plant but by soil microorganisms. To date, mainly aerobic microbial species able to methylate As as an apparent detoxification strategy, have been isolated from paddies. Thus, despite the fact that methylarsenical synthesis appears to be enhanced during anoxic conditions, the drivers and the physiological role of As methylation remain unknown in the absence of oxygen. The thesis focuses on the identification of active As-methylating microorganisms as single species and as members of anaerobic microbiomes from rice paddy soils. In the first part, five bacterial strains and two methanogenic archaea, belonging to genera identified in paddy soils, were evaluated for active arsenite methylation. While aerobic bacterial strains were sensitive to increasing As concentrations, they efficiently methylated As. Conversely, anaerobic bacterial strains were resistant to increasing As concentrations but methylated poorly. Suspecting that As detoxification was occurring through As efflux and outcompeting methylation under anaerobic conditions, we proceeded with the deletion of the arsenite transmembrane transporter in the anaerobic strain Clostridium pasteurianum. The As efflux was disrupted in the mutant leading to higher intracellular concentrations, higher arsM transcription, and increase in the methylation efficiency. Based on the results, we hypothesize that under anoxic conditions, the efficient arsenite efflux systems from anaerobic microorganisms preclude efficient As methylation. In the second part, meta-omic approaches (metagenomics, metatranscriptomics and metaproteomics) were used to identify active As methylators in two soil-derived microbiomes shown to methylate arsenite. The metagenomic data was used to reconstruct the microbial genomes present as metagenome-assembled genomes (MAG). The metabolic capacity for each MAG was identified by the functional annotation of genes while active metabolisms were deciphered from mRNA transcripts (metatranscriptome) and protein expression (metaproteome). Annotation and expression of arsenic resistance genes pointed to fermenting microorganisms as the main drivers of As methylation in both microbiomes. This work is a contribution to the understanding of the linkages between microbial diversity and arsenic bio-transformation.

EPFL2020

Variability in arsenic methylation efficiency across aerobic and anaerobic microorganisms

Rizlan Bernier-Latmani, Karin Lederballe Meibom, Karen Elda Viacava Romo, Arnaud Michel Gelb, Leia Soraya Véronique Falquet, Shannon Eliot Dyer, Adrien Mestrot

Microbially-mediated methylation of arsenic (As) plays an important role in the As biogeochemical cycle, particularly in rice paddy soils where methylated As, generated microbially, is translocated into rice grains. The presence of the arsenite (As(III)) methyltransferase gene (arsM) in soil microbes has been used as an indication of their capacity for As methylation. Here, we evaluate the ability of seven microorganisms encoding active ArsM enzymes to methylate As. Amongst those, only the aerobic species were efficient methylators. The anaerobic microorganisms presented high resistance to As exposure, presumably through their efficient As(III) efflux, but methylated As poorly. The only exception were methanogens, for which efficient As methylation was seemingly an artifact of membrane disruption. Deletion of an efflux pump gene (acr3) in one of the anaerobes, Clostridium pasteurianum, rendered the strain sensitive to As and capable of more efficiently methylating As. Our results led to the following conclusions: (i) encoding a functional ArsM enzyme does not guarantee that a microorganism will actively drive As methylation in the presence of the metalloid and (ii) there is an inverse relationship between efficient microbial As efflux and its methylation, because the former prevents the intracellular accumulation of As.

2020

Properties of Enzymes Involved in Tetrachloroethene Respiration

Géraldine Florence Buttet

Tetrachloroethene (PCE) pollution threatens nature and human health due to its toxic and carcinogenic potential. Due to industrial activities, large amounts of PCE were discharged into the environment over the last decades and represent one of major groundwater pollutants. Organohalide respiration (OHR) is a bacterial anaerobic respiration in which the halogenated compounds, such as chloroethenes, are used as terminal electron acceptors. This process requires the presence of an electron transport chain located in the cytoplasmic membrane which allows proton translocation and establishes a proton-motive force across the membrane. Redox proteins and other non-protein electron shuttles are usually combined in the membrane to accomplish that task. In members of the genera Desulfitobacterium and Dehalobacter, which represent a paradigmatic group of organohalide-respiring bacteria (OHRB), the pceABCT gene cluster has been identified as responsible for PCE respiration, and can be considered as a model system for studying OHR. While the function of PceA, the key enzyme of this process, and PceT, the dedicated chaperon, are well established, it is very likely that PceB plays the role of membrane anchor for PceA. The remaining gene, pceC, codes for a predicted membrane-bound flavoprotein harboring conserved cysteine motifs in the transmembrane domain. Despite the fact that it has been considered as a putative transcriptional regulator, PceC presents all the features that could potentially fulfill the role of electron shuttle between reduced menaquinones and PceA. In the Laboratory for Environmental Biotechnology, a bacterial consortium (SL2-PCEb) and derived subcultures thereof has been used as a model OHRB community. SL2-PCEb has been previously characterized for its stepwise dechlorination of PCE to cis-DCE via a significant accumulation of TCE. Two derived subcultures, named SL2-PCEc and SL2-TCE, harbor a distinct population of Sulfurospirillum sp. (SL2-1 and SL2-2, respectively). Both subcultures showed a different pattern of dechlorination, as strain SL2-1 was only able to dechlorinate PCE to trichloroethene (TCE), while strain SL2-2 kept the potential of the parental consortium, namely PCE to cis-DCE, however, without TCE accumulation. The key enzyme in the consortium SL2-PCEc is known as PceATCE and displays 92% amino acid sequence identity with the well-characterized PceA enzyme from S. multivorans. The overall goal of this thesis was to provide new insights into the physiology and biochemistry of tetrachloroethene-respiring bacteria, to characterize at the biochemical level a new reductive dehalogenase identified from a bacterial consortium, and to assess the kinetic parameters of strains present in this consortium and competing for tetrachloroethene. Finally, the characterization of PceC, a predicted membrane-bound flavoprotein was undertaken.

EPFL2017

ATP Synthesis Coupling in Cells

Explores ATP synthesis in anaerobic cells, coupling reactions for energy production.

Food Biotechnology: Fermented Foods and Microbial Consortia ENG-436: Food biotechnology

Delves into fermented foods, umami taste, taste receptors, and microbial consortia in food biotechnology.

Food Fermentation Technology ENG-436: Food biotechnology

Delves into the science of food fermentation, covering lactose metabolism, soy food fermentation, human milk production, kimchi making, and bacteria isolation.