Melatonin, an underestimated natural substance with great potential for agricultural application

Melatonin (MEL) was thought to be only a neurotransmitter found in vertebrates until its detection in other organisms including plants. Although the number of publications on MEL function in plants is expanding, the knowledge of this subject is still insufficient. Among many functions which MEL performs in plants, its role as an antioxidant and a growth promoter is most supported by experimental evidence. This compound is an independent plant growth regulator and it may mediate the activities of other plant growth regulators. Due to its antioxidant properties MEL may also stabilize cell redox status and protect tissues against reactive oxygen and nitrogen species which accumulated under stressful environment. Some researchers propose that MEL could be used to improve the phytoremediation efficiency of plants against different pollutants. In this paper we show that exogenous MEL applied into the seeds could be a good biostimulator improving not only seed germination, seedling/plant growth but also crop production especially under stress conditions. We also believe that this compound can increase food quality (the aspect of functional food) and may improve human health. Since MEL is inexpensive and safe for animals and humans its application as a biostimulator could be a good, feasible and cost-effective method useful in agriculture.     

Long-term impact of an invertebrate predator, Heterocope septentrionalis, on an arctic pond zooplankton community

1. A long-term field experiment to determine what forces structure and maintain the large-bodied zooplankton assemblages in ponds which lack visual predators was undertaken at the Toolik Lake Research Station in arctic Alaska. Predatory copepods, Heterocope septentrionalis, were introduced to a pond that lacked both fish and invertebrate predators, but contained small- to medium-sized zooplankton, Bosmina longirostris , Daphnia pulex , and Diaptomus pribilofensis. A second pond, which also lacked any predators but had a population of B. longirostris , but no other abundant species, served as a reference population for B. longirostris.
2. The introduction of H. septentrionalis caused the extinction of D. pulex within 1 year and drove B. longirostris to extremely low densities within 4 years. The population of B. longirostris in the reference pond fluctuated throughout the study period, but remained above five individuals per litre. This experiment demonstrates that H. septentrionalis , under natural conditions, made a numerical response to abundant prey and had the capacity to eliminate or reduce vulnerable prey populations of small- to medium-sized zooplankton.     

From intervention to impact: modelling the potential mortality impact achievable by different longlasting, insecticide-treated net delivery strategies

ABSTRACT: BACKGROUND: The current target of universal access to long-lasting, insecticide-treated nets (LLIN) is 80% coverage to reduce malaria deaths by 75% by 2015. So far, campaigns have been the main channel for large-scale delivery of LLINs, however the World Health Organization has recommended that equal priority should be given to delivery via routine antenatal care (ANC) and immunization systems (EPI) to target pregnant women and children from birth. These various channels of LLIN delivery are targeted to children of different ages. Since risk of mortality varies with child age and LLIN effectiveness declines with net age, it was hypothesized that the age at which a child receives a new LLIN, and therefore the delivery channel, is important in optimizing the health impact of a net. METHODS: A simple dynamic mathematical model was developed of delivery and impact of LLINs among children under five years of age and their household members, incorporating data on age-specific malaria death rates, net use by household structure, and net efficacy over time. RESULTS: The presented analysis finds that supplementing a universal mass campaign with extra ANC delivery would achieve a 1.4 times higher mortality reduction than campaign delivery alone, reflecting that children born in the years between campaigns would otherwise have access to old nets or no nets at an age of high risk. The relative advantage of supplementary ANC delivery is still present though smaller if malaria transmission levels are lower or if there is a strong mass effect achieved by mass campaigns. CONCLUSION: These results indicate that LLIN delivery policies must take into account the age of greatest malaria risk. Emphasis should be placed on supporting routine delivery of LLINs to young children as well as campaigns. Lucy C Okell and Lucy Smith Paintain contributed equally.     

Annual changes of bacterial mortality due to viruses and protists in an oligotrophic coastal environment (NW Mediterranean)

The impact of viruses and protists on bacterioplankton mortality was examined monthly during 2 years (May 2005–April 2007) in an oligotrophic coastal environment (NW Mediterranean Sea). We expected that in such type of system, (i) bacterial losses would be caused mainly by protists, and (ii) lysogeny would be an important type of virus–host interaction. During the study period, viruses and grazers together were responsible for 50.6 ± 40.1% day⁻¹ of bacterial standing stock losses (BSS) and 59.7 ± 44.0% day⁻¹ of bacterial production losses (BP). Over the first year (May 2005–April 2006), protists were the principal cause of bacterial mortality, removing 29.9 ± 20.4% day⁻¹ of BSS and 33.9 ± 24.3% day⁻¹ of BP, whereas viral lysis removed 13.5 ± 17.0% day⁻¹ of BSS and 12.3 ± 12.3% day⁻¹ of BP. During the second year (May 2006–April 2007), viruses caused comparable bacterial losses (29.2 ± 14.8% day⁻¹ of BSS and 40.9 ± 20.7% day⁻¹ of BP) to protists (28.6 ± 25.5% day⁻¹ of BSS and 32.4 ± 20.0% day⁻¹ of BP). In 37% of cases higher losses of BP due to viruses than due to protists were found. Lysogenic infection was detected in 11 of 24 samplings. Contrary to our expectations, lytic infections dominated over the two years, and viruses resulted to be a significant source of bacterial mortality in this oligotrophic site.     

Top-down controls on bacterial community structure: microbial network analysis of bacteria,T4-like viruses and protists

Characterizing ecological relationships between viruses, bacteria and protists in the ocean are critical to understanding ecosystem function, yet these relationships are infrequently investigated together. We evaluated these relationships through microbial association network analysis of samples collected approximately monthly from March 2008 to January 2011 in the surface ocean (0–5 m) at the San Pedro Ocean Time series station. Bacterial, T4-like myoviral and protistan communities were described by Automated Ribosomal Intergenic Spacer Analysis and terminal restriction fragment length polymorphism of the gene encoding the major capsid protein (g23) and 18S ribosomal DNA, respectively. Concurrent shifts in community structure suggested similar timing of responses to environmental and biological parameters. We linked T4-like myoviral, bacterial and protistan operational taxonomic units by local similarity correlations, which were then visualized as association networks. Network links (correlations) potentially represent synergistic and antagonistic relationships such as viral lysis, grazing, competition or other interactions. We found that virus–bacteria relationships were more cross-linked than protist–bacteria relationships, suggestive of increased taxonomic specificity in virus–bacteria relationships. We also found that 80% of bacterial–protist and 74% of bacterial–viral correlations were positive, with the latter suggesting that at monthly and seasonal timescales, viruses may be following their hosts more often than controlling host abundance.     

Induced defenses of loblolly pine, Pinus taeda: potential impact on Dendroctonus frontalis within-tree mortality

Loblolly pine (Pinus taeda L.) produces an induced defensive hypersensitive response in inner bark colonized by the southern pine beetle, Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae), and its associated fungi. Adult beetles forced to colonize the induced response tissue in a laboratory study constructed galleries that were the same length as adults boring in normal phloem. However, each female laid fewer eggs in the induced tissue. Larval and pupal mortality were also higher in this tissue when compared to surrounding phloem. Beetles colonizing trees in response to pheromone baits constructed less gallery and laid fewer eggs in induced tissue than in surrounding normal phloem. These results suggest that the lesions produced by the induced defense system in conifers may not only contain the growth of fungi inoculated into trees during the attack phase of beetle colonization, but may also affect survival of bark beetle progeny.

---

Résumé Une réaction hypersensible de défense a été induite dans les couches profondes de l'écorce de P. taeda colonisée par D. frontalis et le champignon qui lui est associé. Au laboratoire, des adultes, contraints de coloniser les tissus où une réaction hypersensible e été induite, ont foré des galeries de même longueur que celles creusées dans du phloème sain. Cependant les femelles ont pondu moins d'oeufs dans les tissus induits; les mortalités larvaires et nymphales étaient aussi plus fortes dans ce tissu que dans le phloème voisin. Les scolytes, ayant colonisé les arbres après attraction par des pièges à phéromones, forent moins de galeries et pondent moins d'oeufs dans le tissu induit que dans le phloème sain voisin. Ces résultats suggèrent que les lésions, provoquées par le système de défense induit des conifères, peuvent non seulement limiter la croissance du champignon inoculé dans l'arbre au cours de la colonisation des scolytes, mais aussi affecter la survie des descendants dans l'écorce.

     

The impact of mortality on predator population size and stability in systems with stage-structured prey

The relationships between a predator population's mortality rate and its population size and stability are investigated for several simple predator-prey models with stage-structured prey populations. Several alternative models are considered; these differ in their assumptions about the nature of density dependence in the prey's population growth; the nature of stage-transitions; and the stage-selectivity of the predator. Instability occurs at high, rather than low predator mortality rates in most models with highly stage-selective predation; this is the opposite of the effect of mortality on stability in models with homogeneous prey populations. Stage-selective predation also increases the range of parameters that lead to a stable equilibrium. The results suggest that it may be common for a stable predator population to increase in abundance as its own mortality rate increases in stable systems, provided that the predator has a saturating functional response. Sufficiently strong density dependence in the prey generally reverses this outcome, and results in a decrease in predator population size with increasing predator mortality rate. Stability is decreased when the juvenile stage has a fixed duration, but population increases with increasing mortality are still observed in large areas of stable parameter space. This raises two coupled questions which are as yet unanswered; (1) do such increases in population size with higher mortality actually occur in nature; and (2) if not, what prevents them from occurring? Stage-structured prey and stage-related predation can also reverse the 'paradox of enrichment', leading to stability rather than instability when prey growth is increased.     

A microbiologist's odyssey: Bacterial viruses to photosynthetic bacteria

Perspective can be defined as the relationships or relative importance of facts or matters from any special point of view. Thus, my Personal perspective reflects the threads I followed in a 50-year journey of research in the complex tapestry of bioenergetics and various aspects of microbial metabolism. An early interest in biochemical and microbial evolution led to the fertile hunting grounds of anoxygenic photosynthetic bacteria. Viewed as a physiological class, these organisms show remarkable metabolic versatility in that certain individual species are capable of using all the known major types of energy conversion (photosynthetic, respiratory, and fermentative) to support growth. Since such anoxyphototrophs are readily amenable to molecular genetic/biological manipulation, it can be expected that they will eventually provide important clues for unraveling the evolutionary relationships of the several kinds of energy conversion. I gradually came to believe that understanding the evolution of phototrophs would require detailed knowledge not only of how light is converted to chemical energy, but also of a) pathways of monomer production from extracellular sources of carbon and nitrogen and b) mechanisms cells use for integrating ATP regeneration with the energy-requiring biosyntheses of biological macromolecules. Serendipic observation of photoproduction of H₂ from organic compounds by Rhodospirillum rubrum in 1949 led to discovery of N₂ fixation by anoxyphototrophs, and this capacity was later exploited for the isolation of hitherto unknown species of photosynthetic prokaryotes, including the heliobacteria. Recent studies on the reaction centers of the heliobacteria suggest the possibility that these bacteria are descendents of early phototrophs that gave rise to oxygenic photosynthetic organisms.Abbreviations AMP adenosine monophosphate - ADP adenosine diphosphate - ATP adenosine triphosphate - ATPase adenosine triphosphatase - Bchl bacteriochlorophyll - DMSO dimethyl sulfoxide - NADH reduced nicotinamide adenine dinucleotide - nif ^– genes for dinitrogen fixation - Nif^– bacterial mutants incapable of dinitrogen fixation - O/R oxidation/reduction - P_i inorganic orthophosphate - R. capsulatus Rhodobacter capsulatus - R. sphaeroides Rhodobacter sphaeroides - Rps. Rhodopseudomonas - TMAO trimethyl amine-N-oxide Written at the invitation of Govindjee.     

Virio- and bacterioplankton of a small river: Influence that viruses have on the mortality of heterotrophic bacteria

The spatial distribution of virio- and bacterioplankton and the role that viruses play in heterotrophic bacteria elimination was studied in the small Il’d’ River (Rybinskoe Reservoir tributary, Upper Volga). The bacterioplankton abundance and biomass constituted 3.3–19.6 (8.5 on average) million cells/ml and 501–2353 mg/m³ (1054 mg/m³ on average), respectively. The highest abundance was registered for the shallow areas under anthropogenic and zoogenic load. The virus abundance varied from 7.4 to 66.9 million particles/ml, being 30.9 million particles/ml on average. The bacteria: virus ratio was in the range of 1.2–11.0 (4.0 on average); the maximal values were registered for the deepest parts of the river. One infected bacterial cell carried up to 45 virile phages. The virus-induced mortality (VIM) was in the range of 1.1–7.8% (3.7% on average) from daily bacterial production. These data evidenced a high abundance of bacterioplankton in the studied river and an insignificant impact of virus-mediated regulation on bacterial abundance and production.     

Measuring microzooplankton grazing on planktonic marine bacteria by its impact on bacterial production

Grazing on planktonic bacteria by microzooplankton was estimated by separating bacteria from the larger plankton with 1m pore Nuclepore filtration and measuring changes in bacteria in filtered and unfiltered samples over 24 hours. In the absence of grazers, bacteria increased linearly. The regression coefficient of linear increase was used to estimatein situ bacterial production. When grazers were present, the changes in bacteria concentration usually took the form of a linear decline, and grazing was estimated by subtracting the regression coefficient of the unfiltered sample from that of the 1m filtrate. Results from the Essex estuary-coastal system of northern Massachusetts show grazing and production at rates that indicate a daily turnover of the standing crop of bacteria, with highest values in mid-estuarine waters. Experiments on the size distribution of grazing showed that microzooplankton from 1–3m were responsible for most of the observed decrease in bacteria. It was suggested that the basic pattern of linear increase of the bacteria in the absence of grazing reflects density-dependent limitation by substrate present at the outset of the incubation and is indicative of a population that has been maintained around the mid-point of the logistic growth curve by grazing.     

Quantifying ecological filters: the relative impact of herbivory, neighbours, and sediment on an oligohaline marsh

The objective of this experiment was to quantify the relative importance of herbivory, interactions with neighbours and sediment addition as filters in controlling the species present in an oligohaline marsh in southeastern Louisiana, USA. We planted 16 species of wetland plants in 3×3 m plots either inside or outside herbivore exclosures, with or without presence of established vegetation, and with or without added sediment. These species, representing 12 families and diverse morphologies, included herbaceous and woody plants. At the end of the growing season above‐ and below ground biomass were measured. In cleared plots (no neighbours) inside herbivore exclosures, 12 of the 16 species grew well, indicating that they could tolerate the physical conditions in the habitat. Competition significantly reduced the biomass of four of these species (A. calamus, C. occidentalis, P. hemitomon, P. cordata), suggesting that it is the strongest species‐specific filter operating in the marsh. These results confirm the general consensus that competition from existing plants is the strongest filter operating in high biomass habitats, and further imply that competition has the potential to remove 33% of the species from the community. Facilitation occurred for one species, R. corniculata. Herbivory had the largest general effect of reducing biomass, as determined in the full ANOVA model, but on a species‐specific basis, significantly reduced the biomass of only two species (T. distichum, T. domingensis). These results support the emerging view that herbivory is an important filter in coastal wetlands. Although several other studies have argued for the importance of sedimentation in controlling plant species composition in wetlands, we found no effect of sediment addition. Competition and herbivory appear to be two critical biological filters that control plant composition of coastal wetlands, and they must be considered in future studies and restoration efforts along the Gulf of Mexico.     

The impact of short-term predator removal on vole dynamics in an arctic-alpine landscape

During 1991–95, mammalian predators (weasel, Mustela nivalis , stoat, M. erminea , mink, M. vison , and red fox, Vulpes vulpes ) were excluded in late summers from a 2 ha piece of a north Norwegian mountain slope. The exclosure extended from an outpost of luxuriant sub-arctic birch forest to a typical arctic–alpine habitat complex, including productive willow scrublands, tundra heaths, dry ridges and snow-beds. The exclosure thus encompassed the entire range of habitat conditions encountered in a typical north Fennoscandian mountain and tundra landscapes. During 1991–95, the exclosure was predator-proof from late July to late September. In wintertime and in early summer, the exclosure was accessible to mammalian predators. Vole dynamics in the short-term exclosure were compared to dynamics in five reference areas with similar habitat conditions.
In 1991, when vole densities were rising in the area, neither collective vole densities nor densities of individual vole species differed significantly between the exclosure and the replicated controls. Spring densities of voles were never significantly different between the exclosure and the controls. With respect to autumnal densities of voles, however, the exclosure was a statistical outlier in the peak year 1992 and throughout the gradual decline phase of 1993–95. In the peak year, the difference in collective vole densities was modest (30%), but increased to two-fold during the first two decline years and was almost four-fold in the crash year of 1995. The strongest response was displayed by field voles ( Microtus agrestis ), hypothesized to be the pivotal prey species of weasels, especially by females and young individuals, i.e. by the functional categories especially sensitive to mammalian predation. These results are consistent with the hypothesis that predation plays a pivotal role for the regulation of herbivorous mammals in relatively productive arctic–alpine habitats.     

The diversity of bacteria,eukaryotic cells and viruses in an oligotrophic lake

An in situ transmission electron microscopic study of biomass samples concentrated from oligotrophic lake water revealed a variety of virus-infected microbial cells and many free viruses and virus-like particles. The most abundant group of microorganisms in screened and filtered water-column samples were 2 μm or less in diameter, and included representatives of several oligotrophic genera, Prosthecomicrobium, Ancyclobacter, Caulobacter and Hyphomicrobium. Among the prokaryotic host cells, which included both heterotrophs and autotrophs, on the basis of electron microscope observations, approximately 17% were infected with bacteriophage or bore adherent phage particles on their surfaces. Several bacterial morphotypes were observed among the prokaryotic hosts. Water samples passed through a 20-μm Nitex screen allowed us to concentrate and examine the larger host cells as well, including several species of single-celled algae and two amoeba species. The infected algal cells included those Chlorella-like in appearance, photosynthetic flagellates and others that could not be positively identified. About one-third of the eukaryotic cells were infected by viruses that were larger (150–200 nm) and structurally more complex than bacteriophages (50–60 nm). None of the viruses have been isolated, but when 0.2 μm filtrate from a biomass sample was spotted onto lawns of four representative heterotrophs and a Chlorella, the clearing observed was taken as evidence of lysis. Cyanobacterial lawns showed no plaques. Thin sections of two amoeba showed food vacuoles containing what appeared to be virus particles of a type seen in certain prokaryotic and eukaryotic cells in the biomass. Received: 26 January 1996 / Received revision: 10 July 1996 / Accepted: 5 August 1996     

The potential impact of urine-LAM diagnostics on tuberculosis incidence and mortality: A modelling analysis

BackgroundLateral flow urine lipoarabinomannan (LAM) tests could offer important new opportunities for the early detection of tuberculosis (TB). The currently licensed LAM test, Alere Determine TB LAM Ag (‘LF-LAM’), performs best in the sickest people living with HIV (PLHIV). However, the technology continues to improve, with newer LAM tests, such as Fujifilm SILVAMP TB LAM (‘SILVAMP-LAM’) showing improved sensitivity, including amongst HIV-negative patients. It is important to anticipate the epidemiological impact that current and future LAM tests may have on TB incidence and mortality.Methods and findingsConcentrating on South Africa, we examined the impact that widening LAM test eligibility would have on TB incidence and mortality. We developed a mathematical model of TB transmission to project the impact of LAM tests, distinguishing ‘current’ tests (with sensitivity consistent with LF-LAM), from hypothetical ‘future’ tests (having sensitivity consistent with SILVAMP-LAM). We modelled the impact of both tests, assuming full adoption of the 2019 WHO guidelines for the use of these tests amongst those receiving HIV care. We also simulated the hypothetical deployment of future LAM tests for all people presenting to care with TB symptoms, not restricted to PLHIV. Our model projects that 2,700,000 (95% credible interval [CrI] 2,000,000–3,600,000) and 420,000 (95% CrI 350,000–520,000) cumulative TB incident cases and deaths, respectively, would occur between 2020 and 2035 if the status quo is maintained. Relative to this comparator, current and future LAM tests would respectively avert 54 (95% CrI 33–86) and 90 (95% CrI 55–145) TB deaths amongst inpatients between 2020 and 2035, i.e., reductions of 5% (95% CrI 4%–6%) and 9% (95% CrI 7%–11%) in inpatient TB mortality. This impact in absolute deaths averted doubles if testing is expanded to include outpatients, yet remains <1% of country-level TB deaths. Similar patterns apply to incidence results. However, deploying a future LAM test for all people presenting to care with TB symptoms would avert 470,000 (95% CrI 220,000–870,000) incident TB cases (18% reduction, 95% CrI 9%–29%) and 120,000 (95% CrI 69,000–210,000) deaths (30% reduction, 95% CrI 18%–44%) between 2020 and 2035. Notably, this increase in impact arises largely from diagnosis of TB amongst those with HIV who are not yet in HIV care, and who would thus be ineligible for a LAM test under current guidelines. Qualitatively similar results apply under an alternative comparator assuming expanded use of GeneXpert MTB/RIF (‘Xpert’) for TB diagnosis. Sensitivity analysis demonstrates qualitatively similar results in a setting like Kenya, which also has a generalised HIV epidemic, but a lower burden of HIV/TB coinfection. Amongst limitations of this analysis, we do not address the cost or cost-effectiveness of future tests. Our model neglects drug resistance and focuses on the country-level epidemic, thus ignoring subnational variations in HIV and TB burden.ConclusionsThese results suggest that LAM tests could have an important effect in averting TB deaths amongst PLHIV with advanced disease. However, achieving population-level impact on the TB epidemic, even in high-HIV-burden settings, will require future LAM tests to have sufficient performance to be deployed more broadly than in HIV care.

Saskia Ricks and colleagues model the impact of urine-LAM diagnostics for reducing tuberculosis incidence, across different implementation scenarios.     

Short-term variations in abundances and potential activities of viruses,bacteria and nanoprotists in Lake Bourget

Samples were collected at four depths every 6 h over a 42-h period during two contrasting seasons (June vs. December) from Lake Bourget, France, for evidence of circadian fluctuations in the concentrations and potential activities of viruses, prokaryotes and protists in relation to environmental conditions: temperature, chlorophyll a and dissolved organic carbon (DOC) concentrations. Considerable vertical and temporal fluctuations were observed for all variables. Circadian variations were noted for DOC and chlorophyll a concentrations. Despite the external abiotic forcing (light, water movements), the fluctuations of microbial variables (including viruses) in most cases were apparently linked to biotic factors and interactions. Standing stocks and activities, as well as the number and levels of correlations among the microbial components, were, surprisingly, higher in winter than in summer. We speculate that this was because trophic interactions prevailed over the seasonal forcing (i.e. temperature) in shaping the observed differences.     

Ionophore resistance of ruminal bacteria and its potential impact on human health

In recent years, there has been a debate concerning the causes of antibiotic resistance and the steps that should be taken. Beef cattle in feedlots are routinely fed a class of antibiotics known as ionophores, and these compounds increase feed efficiency by as much as 10%. Some groups have argued that ionophore resistance poses the same public health threat as conventional antibiotics, but humans are not given ionophores to combat bacterial infection. Many ruminal bacteria are ionophore-resistant, but until recently the mechanism of this resistance was not well defined. Ionophores are highly lipophilic polyethers that accumulate in cell membranes and catalyze rapid ion movement. When sensitive bacteria counteract futile ion flux with membrane ATPases and transporters, they are eventually de-energized. Aerobic bacteria and mammalian enzymes can degrade ionophores, but these pathways are oxygen-dependent and not functional in anaerobic environments like the rumen or lower GI tract. Gram-positive ruminal bacteria are in many cases more sensitive to ionophores than Gram-negative species, but this model of resistance is not always clear-cut. Some Gram-negative ruminal bacteria are initially ionophore-sensitive, and even Gram-positive bacteria can adapt. Ionophore resistance appears to be mediated by extracellular polysaccharides (glycocalyx) that exclude ionophores from the cell membrane. Because cattle not receiving ionophores have large populations of resistant bacteria, it appears that this trait is due to a physiological selection rather than a mutation per se. Genes responsible for ionophore resistance in ruminal bacteria have not been identified, but there is little evidence that ionophore resistance can be spread from one bacterium to another. Given these observations, use of ionophores in animal feed is not likely to have a significant impact on the transfer of antibiotic resistance from animals to man.     

Chromium-resistant bacteria and cyanobacteria: impact on Cr(VI) reduction potential and plant growth

Two chromium-resistant bacterial strains, Bacillus cereus S-6 and Ochrobactrum intermedium CrT-1, and two cyanobacterial strains, Oscillatoria sp. and Synechocystis sp., were used in this study. At initial chromate concentrations of 300 and 600 μg K₂CrO₄ mL⁻¹, and an inoculum size of 9.6×10⁷ cells mL⁻¹, B. cereus S-6 completely reduced Cr(VI), while O. intermedium CrT-1 reduced Cr(VI) by 98% and 70%, respectively after 96 h. At 100 μg K₂CrO₄ mL⁻¹, Synechocystis sp. MK(S) and Oscillatoria sp. BJ2 reduced 62.1% and 39.9% of Cr(VI), respectively, at 30°C and pH 8. Application of hexavalent chromate salts adversely affected wheat seedling growth and anatomical characters. However, bacterial inoculation alleviated the toxic effects, as reflected by significant improvements in growth as well as anatomical parameters. Cyanobacterial strains also led to some enhancement of various growth parameters in wheat seedlings.