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Mercury (Hg) pollution poses a global threat to human and environmental health due to its noxiousness, mobility, and lengthy residence duration in the atmosphere ( Raphael etal., 2011). Toxic metals rapidly accumulate in the food chain, impacting higher trophic levels, hence these are of principal concern nowadays ( Raphael etal., 2011). According to recent research, oceanic release and biomass burning (organic compounds) account for the majority of worldwide Hg emissions, with anthropogenic activities accounting for the remaining significant percentage ( Pirrone etal., 2010; Nelson etal., 2012; Serrano etal., 2013). Hg exists in elemental, inorganic, and organic forms in both land and water systems, depending on oxidation-reduction conditions. In the atmosphere, Hg with valence +2 is more extensively spread ( Wang etal., 2004). In the biogeochemical cycle, a considerable part of Hg accumulates in seas and oceans by its atmospheric deposition ( Bindler, 2003; Wang etal., 2004). The effects of human-induced sources on the Hg contents and its forms are extensively larger in the photic layers of oceans ( Strode etal., 2007). According to a study by Ozemek et al., healthy diets like DASH dietary patterns have been shown to decrease SBP by 11 mm Hg in hypertensive individuals and by 3 mm Hg in normotensive individuals. Ideally, the goal is to reduce sodium to <1500 mg/dl, but it is good to aim for at least a 1000 mg/day reduction, which has been shown to reduce SBP approximately by 5/6 mm Hg in hypertensive individuals and by 2/3 mm Hg in normotensive individuals [ 11]. Furthermore, Ozemek et al. revealed in their study that increasing dietary potassium intake with a goal of 3500-5000 mg/day has been shown to reduce SBP by −4/5 mm Hg in hypertensive individuals and by −2 mm Hg in normotensive individuals [ 11]. The Mediterranean diet (Med Diet) has also helped lower BP. As per the Maine-Syracuse Longitudinal Study conducted in the United States in 2020 by a group of researchers who followed 851 US older adults, for every one unit increase in the Med Diet score in participants, it was found that there was a corresponding reduction of 0.69 units in SBP, a reduction of 0.33 in DBP, and a reduction of 0.45 on mean arterial pressure (MAP) [ 32]. Although this seems to be small, this change can have a noteworthy effect at the level of the population; that is, a decrease of 2 mm Hg in SBP can lead to a decrease of 10% when it comes to the population [ 32]. According to the observational studies conducted in Mediterranean countries, higher adherence to a Med Diet is associated with a decreased risk of cardiovascular disease, overall mortality as well as neoplastic disease [ 33, 34]. The Med Diet consists of higher consumption of extra virgin olive oil, vegetables, fruits, whole grains, nuts, cereals, as well as seeds; moderate consumption of fish, poultry, red wine, and dairy; and lower consumption of processed foods and red meat [ 35]. Weight loss is one of the most important non-pharmacological interventions to lower BP. Numerous interrelated pathophysiologic mechanisms stimulate higher BP in obesity [ 12]. In overweight/obese individuals, accelerated vascular aging can lead to HTN due to inflammation, oxidative stress, and insulin resistance [ 13]. Obese individuals also experience increased activity of the sympathetic nervous system and the renin-angiotensin-aldosterone system [ 14]. The combined effect results in increased sodium resorption by the kidney, impaired vasodilation, volume expansion, and decreased natriuresis, thus leading to elevated BP [ 15]. Ozemek et al. trials have shown that weight loss helped lower systolic BP in hypertensive individuals by 5 mm Hg and in normotensive individuals by 2 to 3 mm Hg. According to the Centers for Disease Control (CDC), a BMI of 25 to 29.9 is considered overweight, and a BMI of 30 or higher is considered obese. In overweight or obese individuals, achieving their ideal body weight is best, but it is good to aim for at least a 1 kg reduction in body weight. The study by Ozemek et al. also revealed that for every 1 kg reduction in body weight, we can expect about a 1 mm Hg reduction in blood pressure.
The selected isolates were further analyzed by subjecting them to 16S rDNA sequencing. In brief, DNA was isolated and the polymerase chain reaction (PCR) amplification was executed with the universal 16S rDNA primers of 27F (5’-AGAGTTTGATCMTGGCTCAG-3’) and 1495R (5’-GGHTACCTTGTTACGACTT-3’) as described by Dash and Das (2014). The amplified PCR products were sequenced and submitted to NCBI, as described by Kumar etal. (2018). The detailed procedure is elaborated in the SI. Genotyping of merA gene It can be observed that high Hg concentration causes structural deformities which may be due to its toxic nature. In our previous study, we reported that cultures accustomed to grow in the presence of HgCl 2 manifested major morphological abnormalities ( Joshi etal., 2021). We also suggested several structural asymmetries allied with the cell wall and cytoplasmic membrane, significantly affecting the cellular mechanism. Resultantly, there is a substantial delay at the beginning of growth and cell division in a higher concentration of Hg 2+. Metabolites formed during Hg (II) reduction In prior studies, many pathways have been reported for Hg 2+ detoxification in microbes using various tools and technologies ( Chang etal., 2020; Cursino etal., 2000; Chang etal., 2021). In the present study, a metabolic pathway is hypothesized based on the GC-MS metabolites and protein-ligand interaction ( Figure S6) and an attempt has been made to correlate the proposed pathway with the different components of the already existing pathways. In this preliminary study, we found that general resistance/detoxification mechanisms of NIOT-EQR_J248 and NIOT-EQR_J251 in response to inorganic mercury (Hg 2+) exposure were a multisystem combined process. The modification in functional groups present in the culture pellets was identified by measuring the spectra in the range of 400 to 4000 cm -1 using Fourier transform infrared (FT-IR) spectroscopy (IR Affinity-I spectrometer, Shimadzu, Japan), as described by Joshi etal. (2021). In brief, 48 h grown cultures in ZMB medium without Hg supplementation were used as a control, whereas cultures with 50 mg/L of Hg supplementation were used as Hg treated. The mixtures (lyophilized cells and 2% KBr) were fixed in the FT-IR spectrometer after compressing them into translucent sample discs, followed by analyzing in ATR-FT-IR mode by following the manufacturer’s protocol. Scanning Electron Microscopy (SEM) analysis of MRBGJ: Conceptualization, Methodology, Formal analysis, Investigation, Writing-original draft, Writing-review & editing. PV: Investigation, Formal analysis, Writing-review & editing. BM: Investigation. PG: Formal analysis. DMP: Investigation. DKJ: Writing-review & editing. NVV: Supervision, Project administration, Writing-review & editing. GD: Supervision, Project administration, Writing-review & editing. All authors contributed to the article and approved the submitted version. Funding Increased physical activity has been advocated as the first-line intervention for preventing and treating patients with prehypertension and as a treatment strategy for patients with stage 1 or stage 2 HTN, according to the Duthe American College of Sports Medicine, the United States Joint Nations Committee on Prevention, Detection, Evaluation, and Treatment of High BP, the World Health Organization and International Society of Hypertension, and The National Heart Foundation [ 36]. Exercise can consequently help prevent prehypertension from progressing and can help reduce or stop medications prescribed for the treatment of stage 1 HTN [ 37]. One of the quintessential steps to manage HTN is lifestyle modifications like exercise, weight loss, dietary interventions, a low-sodium diet, limiting alcohol consumption, smoking cessation, and stress management to help control BP. The treatment of HTN is based on specific characteristics like stage of disease, compliance, and comorbid conditions. For proper management of HTN, we may need to include pharmacological and non-pharmacological interventions [ 5]. Despite advancements in medicine and treatment options, the global burden of HTN has been increasing due to the advancing age of the population and an increasing prevalence of obesity. HTN is an insidious disease that, if not treated promptly, predisposes us to cardiovascular complications and various other complications [ 6]. Increased physical activity, limiting salt intake, minimizing alcohol consumption, smoking cessation, and stress management together support the management of patients with HTN and as preventive measures in the general population [ 7]. However, it is important to note that lifestyle modification is a process that requires patients to adhere continuously [ 5]. Although weight loss plays a significant role in lowering BP, it may be challenging to stay constantly motivated for long-term results [ 28]. Developing strategies to identify individuals who are unable to maintain lifestyle changes may be crucial to help them stay motivated to achieve weight management goals [ 28]. Furthermore, in recent times, an effective tool to promote the maintenance of healthy lifestyle changes like weight loss can be the use of mobile technology and personal digital devices, especially when individuals no longer have the availability of support and accountability through active interventions [ 29]. In hypertensive individuals with normal weight, other interventions like the DASH diet help lower BP [ 28].
To inspect the consequence of Hg 2+ concentration on the morphology, the bacterial cells were freshly grown in the presence (50 and 100 mg/L - test samples) and absence (control) of Hg 2+ as HgCl 2; and cell pellets were harvested by centrifugation (5000 rpm at 4°C for 5 min) after 48 h. SEM analysis has been carried out, as reported by Joshi etal. (2021). In brief, the bacterial cells were fixed with 2.5% glutaraldehyde followed by the post-fixing in 1% osmium tetroxide and dehydration of the cells with graded ethanol series (25%, 50%, 80%, 90%, and absolute). The processed samples were scanned using SEM (JEOL-JSM-IT500). Extraction of metabolites and Gas Chromatography-Mass Spectrometry (GC-MS) analysis
Publisher’s note
Gajendra Joshi 1* Pankaj Verma 2 Balakrishnan Meena 1 Prasun Goswami 1† D Magesh Peter 2 Dilip Kumar Jha 2 Nambali Valsalan Vinithkumar 1 Gopal Dharani 2 The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Publisher’s note Intermittent fasting (IF) is an effective way to lose weight and thus helps lower blood pressure [ 10]. The mechanism by which IF lowers BP may be due to a brain-derived neurotrophic factor (BDNF)-induced increase in parasympathetic activity [ 16]. Increased excretion of norepinephrine and increased sensitivity of insulin and natriuretic peptides also play a role [ 16]. The activation of glutamatergic receptors produces BDNF [ 10]. IF also stimulates the release of BDNF [ 10]. BDNF, in turn, stimulates the cholinergic neurons to release acetylcholine, which via the vagus nerve, controls the cardiac function to the sinoatrial (SA) node, causing a reduction of heart rate [ 17]. Also, blood vessels are expanded by the neurotransmitter, leading to a reduction in BP [ 18]. The pathogenesis of blood pressure lowering by activation of the parasympathetic nervous system involves the role of the cerebrospinal stem in the activation of cholinergic neurons [ 19, 20]. However, cardiovascular health benefits have only been observed to last as long as the IF diet lasted and pressures returned to initial values after the completion of the IF diet [ 21]. Toledo et al. performed a study in Germany in which 1422 participants on the IF diet were followed up for one year [ 16]. These participants had a fasting period of four to 21 days, which involved 200-250 kcal daily meals [ 16]. In participants who fasted for a longer time, a reduction of SBP and DBP was observed [ 16]. The statistical analysis of Hg removal potential among the different species i.e., Alcanivorax xenomutans, Halomonas sp., Marinobacter hydrocarbonoclasticus and within the Halomonas spp. revealed that the Hg removal by NIOT-EQR_J251 was significantly higher (p< 0.01) than NIOT-EQR_J7 and NIOT-EQR_J258. There was a significant difference (p< 0.05) in the removal of Hg between NIOT-EQR_J248 vs. NIOT-EQR_J258 and NIOT-EQR_J248 vs. NIOT-EQR_J251. Al-Mailem etal. (2011) reported Haloferax sp. (HA1 and HA2), Halobacterium sp. HA3, and Halococcus sp. HA4 effectively volatilized (from 40 to 65%) the available 100 mg/L of Hg after 8 days. Many other isolates such as Bacillus sp., Pseudomonas stutzeri, Pseudomonas putida, Vibrio fluvialis could volatilize 60%-95%, 94%, 100%, 60% of Hg 2+, respectively, from culture ( Zhang etal., 2012; Dash etal., 2013; Giri etal., 2014; Saranya etal., 2017; Zheng etal., 2018).
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