Introduction: Thyroid epithelial cells produce moderate amounts of reactive oxygen species that are physiologically required for thyroid hormone synthesis. Nevertheless, when they are produced in excessive amounts, they may become toxic. Objective: The present study is aimed to compare the lipid peroxidation (LPO), antioxidant enzymes – superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and non-protein thiols (reduced glutathione (GSH)) in human thyroid tissues with malignant and non-malignant disorders. Design and Methods: The study used human thyroid tissues and blood samples from 157 women (147 diseased and 10 normal). Thyroid hormones, oxidative stress markers and antioxidants were estimated by standard methods. Results: LPO significantly increased in most of the papillary thyroid carcinoma (PTC: 82.9%) and follicular thyroid adenoma (FTA: 72.9%) tissues, whilst in a majority of nodular goitre (69.2%) and Hashimoto’s thyroiditis (HT: 73.7%) thyroid tissues, it remained unaltered. GSH increased in PTC (55.3%), remained unaltered in FTA (97.3%) and all other goiter samples studied. SOD increased in PTC (51.1%) and all other malignant thyroid tissues studied. CAT remained unaltered in PTC (95.7%), FTA (97.3%) and all other non-malignant samples (HT, MNG, TMNG) studied. GPx increased in PTC (63.8%), all other malignant thyroid tissues and remained unaltered in many of the FTA (91.9%) tissues and all other non-malignant samples (HT, MNG, TMNG) studied. Conclusions: In the case of non-malignant thyroid tumours, the oxidant–antioxidant balance was undisturbed, whilst in malignant tumours the balance was altered, and the change in r value observed in the LPO and SOD pairs between normal and PTC tissues and also in many pairs with multi-nodular goitre (MNG)/toxic MNG tissues may be used as a marker to differentiate/detect different malignant/non-malignant thyroid tumours.

oxidizing bacteria capable of fixing atmospheric nitrogen were isolated from garden soil, pond mud, oil field soil, and soil exposed to natural gas, indicating a rather wide prevalence in nature. This may explain the high concentration of organic nitrogen commonly found in soils exposed to gas leakage from pipelines or natural-gas seeps. Added molybdenum was a requirement for growth in a nitrogen-free mineral salts medium. All nitrogenfixing, methane-oxidizing bacteria isolated were gram-negative, nonsporeforming, usually motile rods. Colonies were light yellow, yellow, or white. The most common isolate, which formed lightyellow colonies, is referred to as Pseudomonas

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