Alternatives to the Calvin Cycle and the Krebs Cycle in Anaerobic Bacteria: Pathways with Carbonylation Chemistry

Students often struggle to understand the complex molecular systems and processes presented in introductory biology courses. These include the Calvin cycle, the Krebs cycle, transcription and translation, and DNA replication, among others. Traditionally, these systems and processes are taught using textbook readings and PowerPoint slides as lecture aids; video animations have also become popular in recent years. Students tend to be passive observers in many of these methods of instruction, relying heavily on “memorization” learning techniques. To address this, I developed an active-learning intervention called “molecular sculpting” in which students construct two-dimensional or three-dimensional versions of an assigned molecular system or process, complete with representations of proteins, chromosomes, electrons, protons, and other molecules (depending on the system). The value of this learning activity was measured in five class sessions in an introductory biology course during the 2014–2015 academic year. Pre- and post-class written assignments showed that students were often able to describe course concepts more completely after sessions in which sculpting was used, compared with sessions without sculpting. Molecular sculpting is a unique, hands-on activity that appears to have significant learning gains associated with it; it can be adapted for use in a variety of K–14 biology courses.

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The drug ornidazole inhibits photosynthesis in a different mechanism described for protozoa and anaerobic bacteria

Biochemical Journal ◽

10.1042/bcj20160433 ◽

2016 ◽

Vol 473 (23) ◽

pp. 4413-4426 ◽

Cited By ~ 5

Author(s):

Yehouda Marcus ◽

Noam Tal ◽

Mordechai Ronen ◽

Raanan Carmieli ◽

Michael Gurevitz

Keyword(s):

Electron Transport ◽

Nitro Group ◽

Bacterial Infections ◽

Electron Tunneling ◽

Anaerobic Bacteria ◽

Calvin Cycle ◽

Photosynthetic Electron Transport ◽

Iron Sulfur Cluster ◽

Efficient Inhibitor ◽

Oxygen Photoreduction

Ornidazole of the 5-nitroimidazole drug family is used to treat protozoan and anaerobic bacterial infections via a mechanism that involves preactivation by reduction of the nitro group, and production of toxic derivatives and radicals. Metronidazole, another drug family member, has been suggested to affect photosynthesis by draining electrons from the electron carrier ferredoxin, thus inhibiting NADP+ reduction and stimulating radical and peroxide production. Here we show, however, that ornidazole inhibits photosynthesis via a different mechanism. While having a minute effect on the photosynthetic electron transport and oxygen photoreduction, ornidazole hinders the activity of two Calvin cycle enzymes, triose-phosphate isomerase (TPI) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Modeling of ornidazole's interaction with ferredoxin of the protozoan Trichomonas suggests efficient electron tunneling from the iron–sulfur cluster to the nitro group of the drug. A similar docking site of ornidazole at the plant-type ferredoxin does not exist, and the best simulated alternative does not support such efficient tunneling. Notably, TPI was inhibited by ornidazole in the dark or when electron transport was blocked by dichloromethyl diphenylurea, indicating that this inhibition was unrelated to the electron transport machinery. Although TPI and GAPDH isoenzymes are involved in glycolysis and gluconeogenesis, ornidazole's effect on respiration of photoautotrophs is moderate, thus raising its value as an efficient inhibitor of photosynthesis. The scarcity of Calvin cycle inhibitors capable of penetrating cell membranes emphasizes on the value of ornidazole for studying the regulation of this cycle.

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Application of commercial test-systems to identify gram-negative facultatively anaerobic bacteria

Agricultural science and practice ◽

10.15407/agrisp3.01.043 ◽

2016 ◽

Vol 3 (1) ◽

pp. 43-48 ◽

Cited By ~ 1

Author(s):

V. Patyka ◽

L. Butsenko ◽

L. Pasichnyk

Keyword(s):

Erwinia Amylovora ◽

Anaerobic Bacteria ◽

Biochemical Properties ◽

Test System ◽

Phytopathogenic Bacteria ◽

Gram Negative ◽

Test Systems ◽

Facultatively Anaerobic ◽

Microbiological Methods

Aim. To validate the suitability of commercial API 20E test-system (bioMerieux) for the identifi cation and characterization of facultative gram-negative phytopathogenic bacterial isolates. Methods. Conventional mi- crobiological methods, API 20E test-system (bioMerieux) according to the manufacturer’s instructions. Re- sults. The identifi cation results for Erwinia amylovora, Pectobacterium carotovorum and Pantoea agglome- rans isolates were derived from the conventional and API 20E test systems, which, were in line with the literature data for these species. The API 20E test-system showed high suitability for P. agglomerans isolates identifi cation. Although not all the species of facultatively anaerobic phytopathogenic bacteria may be identi- fi ed using API 20E test-system, its application will surely allow obtaining reliable data about their physiologi- cal and biochemical properties, valuable for identifi cation of bacteria, in the course of 24 h. Conclusions. The results of tests, obtained for investigated species while using API 20E test-system, and those of conventional microbiological methods coincided. The application of API 20E test-system (bioMerieux) ensures fast obtain- ing of important data, which may be used to identify phytopathogenic bacteria of Erwinia, Pectobacterium, Pantoea genera.

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