Biocide Treatment Research Articles

Peracetate/singlet oxygen chemistry used in post-bleaching of kraft pulp as a practical oxidant for paper machines

The use of a novel sodium peracetate/singlet oxygen chemistry for brightening bleached kraft pulp shows exciting potential for technical performance, supply logistics, safety, and cost reduction. Potential chemical carryover to the paper machine raises questions about whether peracetate will impact paper machine performance, such as metal corrosion, useful press felt life, and interference with existing biocide programs or paper machine chemistry. Sodium peracetate/singlet oxygen chemistry can be used in high-density storage chests for brightening/whitening and to increase color stability. Any oxidant used directly before the paper machine has the possibility of impacting paper machine operations. Traditional oxidants used in bleaching, such as chlorine dioxide and hydrogen peroxide, are known to cause corrosion on machinery metals and press felts. Hydrogen peroxide residuals can interfere with common biocide programs. Traditional oxidants used in biocide treatments themselves significantly degrade press felt life when the rule-of-thumb concentration thresholds are exceeded. Sodium peracetate is evaluated in this paper for its impact on nylon press felt fiber degradation, metal corrosion, and interference with typical biocide programs. Laboratory results indicate that sodium peracetate/singlet oxygen chemistry is less corrosive than chlorine, bro-mine, and hydrogen peroxide on press felt nylon fiber and can therefore be used at higher levels than those chemistries to increase brightness without increasing negative downstream impact. Sodium peracetate can also be used with current biocide programs without negative impacts such as consumptive degradation. Higher residuals of per-acetate going to the paper machine may be useful as a biocide itself and can complement existing programs, allowing those programs to stay within their safe operating levels and thereby extend press felt useful life.

The Effects of Chemical and Mechanical Stresses on Bacillus cereus and Pseudomonas fluorescens Single- and Dual-Species Biofilm Removal

Biofilm control is mainly based on chemical disinfection, without a clear understanding of the role of the biocides and process conditions on biofilm removal. This study aims to understand the effects of a biocide (benzyldimethyldodecyl ammonium chloride—BDMDAC) and mechanical treatment (an increase of shear stress -) on single- and dual-species biofilms formed by Bacillus cereus and Pseudomonas fluorescens on high-density polyethene (HDPE). BDMDAC effects were initially assessed on bacterial physicochemical properties and initial adhesion ability. Then, mature biofilms were formed on a rotating cylinder reactor (RCR) for 7 days to assess the effects of chemical and mechanical treatments, and the combination of both on biofilm removal. The results demonstrated that the initial adhesion does not predict the formation of mature biofilms. It was observed that the dual-species biofilms were the most susceptible to BDMDAC exposure. The exposure to increasing emphasised the mechanical stability of biofilms, as lower values of (1.66 Pa) caused high biofilm erosion and higher values (17.7 Pa) seem to compress the remaining biofilm. In general, the combination of BDMDAC and the mechanical treatment was synergic in increasing biofilm removal. However, these were insufficient to cause total biofilm removal (100%; an average standard deviation of 11% for the method accuracy should be considered) from HDPE.

Dark-pigmented biodeteriogenic fungi in etruscan hypogeal tombs: New data on their culture-dependent diversity, favouring conditions, and resistance to biocidal treatments

Subterranean Cultural Heritage sites are frequently subject to biological colonization due to the high levels of humidity, even in conditions of low irradiance and oligotrophy. Here microorganisms form complex communities that may be dangerous through mineral precipitation, through the softening of materials or causing frequent surface discolorations. A reduction of contamination’s sources along with the control of microclimatic conditions and biocide treatments (overall performed with benzalkonium chloride) are necessary to reduce microbial growths. Dark discolorations have been recorded in the painted Etruscan tombs of Tarquinia, two of which have been analyzed to collect taxonomical, physiological, and ecological information. Eighteen dark-pigmented fungi were isolated among a wider culturable fraction: nine from blackening areas and nine from door sealings, a possible route of contamination. Isolates belonged to three major groups: Chaetothyriales, Capnodiales (Family Cladosporiaceae), and Acremonium-like fungi. Exophiala angulospora and Cyphellophora olivacea, a novelty for hypogea, were identified, while others need further investigations as possible new taxa. The metabolic skills of the detected species showed their potential dangerousness for the materials. Their tolerance to benzalkonium chloride-based products suggested a certain favouring effect through the decreasing competitiveness of less resistant species. The type of covering of the dromos may influence the risk of outer contamination. Fungal occurrence can be favoured by root penetration.

Comparison of characteristic components in tea-leaves fermented by Aspergillus pallidofulvus PT-3, Aspergillus sesamicola PT-4 and Penicillium manginii PT-5 using LC-MS metabolomics and HPLC analysis

Microbiota influenced quality formation of ripened Pu-erh tea. To understand the effect of each tea-derived fungal strain, tea-leaves were fermented by Aspergillus pallidofulvus PT-3 (ApaPT), Aspergillus sesamicola PT-4 (AsePT) and Penicillium manginii PT-5 (PmaPT), respectively. 14 Phenolic compounds, 3 purine alkaloids, 19 free amino acids and γ-aminobutyric acid contents were determined by HPLC and amino acid analyzer analysis. Additionally, UHPLC-Q-TOF/MS method was developed for LC-MS metabolomics analysis. Multivariate statistical analyses, such as PCA and HCA, exhibited that the chemical profile of PmaPT fermentation was similar to biocidal treatment, but had significant differences with ApaPT and AsePT fermentation. The differentiated metabolites (VIP > 1, p < 0.05 and FC > 1.50 or < 0.66) and one-way ANOVA revealed the impact of three fungal strains in tea-leaves fermentation. APaPT and AsePT contributed to biosynthesis of gallic acid and several flavonoids, such as kaempferol, quercetin and myricetin in the metabolism of phenolic compounds.

Crucial Role of ppGpp in the Resilience of Escherichia coli to Growth Disruption.

Bacteria grow in constantly changing environments that can suddenly become completely depleted of essential nutrients. The stringent response, a rewiring of the cellular metabolism mediated by the alarmone (p)ppGpp, plays a crucial role in adjusting bacterial growth to the severity of the nutritional stress. The ability of (p)ppGpp to trigger a slowdown of cell growth or induce bacterial dormancy has been widely investigated. However, little is known about the role of (p)ppGpp in promoting growth recovery after severe growth inhibition. In this study, we performed a time-resolved analysis of (p)ppGpp metabolism in Escherichia coli as it recovered from a sudden slowdown in growth. The results show that E. coli recovers by itself from the growth disruption provoked by the addition of serine hydroxamate, the serine analogue that we used to induce the stringent response. Growth inhibition was accompanied by a severe disturbance of metabolic activity and, more surprisingly, a transient overflow of valine and alanine. Our data also show that ppGpp is crucial for growth recovery since in the absence of ppGpp, E. coli's growth recovery was slower. In contrast, an increased concentration of pppGpp was found to have no significant effect on growth recovery. Interestingly, the observed decrease in intracellular ppGpp levels in the recovery phase correlated with bacterial growth, and the main effect involved in the return to the basal level was identified by flux calculation as growth dilution. This report thus significantly expands our knowledge of (p)ppGpp metabolism in E. coli physiology.IMPORTANCE The capacity of microbes to resist and overcome environmental insults, known as resilience, allows them to survive in changing environments but also to resist antibiotic and biocide treatments and immune system responses. Although the role of the stringent response in bacterial resilience to nutritional stresses has been well studied, little is known about its importance in the ability of the bacteria to not just resist but also recover from these disturbances. To address this important question, we investigated growth disruption resilience in the model bacterium Escherichia coli and its dependence on the stringent response alarmone (p)ppGpp by quantifying ppGpp and pppGpp levels as growth was disrupted and then recovered. Our findings may thus contribute to understanding how ppGpp improves E. coli's resilience to nutritional stress and other environmental insults.

Assessment of the microbial community and biocide resistance profile in production and injection waters from an Andean oil reservoir in Colombia

Water flooding is a widely applied method for secondary oil recovery. However, this practice introduces exogenous microorganisms into the oil reservoirs that can have deleterious consequences for the recovery process, such as hydrogen sulfide production and corrosion. Biocide treatments have been used to control harmful microbial activity. However, they tend to has limited efficacy attributed to the selection of resistant bacterial populations. This work combines Metagenomic and metataxonomic approaches to investigate the phylogenetic and functional profile of the produced and injected water from an oil reservoir located in the Andean region. The results reveal a marked dominance of the phylum Proteobacteria in both samples (nearly 99%). While Arcobacter sp. and Pseudomonas balearica were the dominant microbes in the injected water, Marinobacter sp. and Arcobacter sp. were the dominant bacteria in the produced water. Biocide resistance genes coding for efflux pumps and transporters were enriched in the injected water that is treated with a mixture of glutaraldehyde and THPS. The draft genome of the Pseudomonas balearica of the injection water encodes several proteins related to efflux pumps, while the Arcobacter sp. draft genome showed fewer proteins related to these resistance systems. Genome annotation of gene clusters related to secondary metabolism also showed that the Pseudomonas balearica present gene clusters for Amonabactin, Ectoine, and dipeptide N-acetyl glutaminyl glutamine amide (NAGNN), whereas the Arcobacter sp. possess one gene cluster for Bacteriocin.

No Clear Response in the Stormwater Phytoplankton Community to Biocide Contamination

This study investigated the responses of natural phytoplankton communities of an urban stormwater pond to biocide contamination. The biocides carbendazim, terbutryn, diuron, and irgarol 1051, and their mixture, were used in two laboratory microcosm and one outdoor mesocosm studies at concentrations of 10, 100, and 1000 ng L−1. The water samples were collected in a pond receiving significant biocide contamination. The mesocosm study was carried out in the same pond. The phytoplankton community response was evaluated after 10–15 days of exposure, with respect to its taxonomic composition, abundance and biovolume. No significant changes were observed in any of the experiments. Only at the highest applied terbutryn concentration were lower numbers of taxa identified in both microcosm and mesocosm experiments. Additionally, increases in Chlorophyta abundance and biovolume, along with an increase in irgarol concentration, were observed throughout the three experiments. Nevertheless, the statistical analysis did not confirm any significant differences among the biocide treatments. These results suggest that the biocide concentrations probably were below the harmful or toxic threshold to the stormwater pond phytoplankton. On the other hand, as the investigated pond phytoplankton taxa face biocide inputs throughout the year, they could have already adapted to the tested biocide contamination.

Changes in heterotrophic microbial communities induced by biocidal treatments in the Monastery of San Martiño Pinario (Santiago de Compostela, NW Spain)

Previous studies have provided evidence that chemical biocides can condition the behaviour of microbial populations, thereby promoting recolonization by some groups of microorganisms. We conducted a year-long study to evaluate the extent to which fungal and bacterial communities are affected by the biocidal treatments Biotin R®, Biotin T®, Preventol RI80®, New Des 50®, benzalkonium chloride and an ethanol-water (1:1) mixture, used to remove Apatococcus lobatus from the granite walls of the San Martiño Pinario Monastery in Santiago de Compostela (NW Spain). Bacterial, fungal, algal and cyanobacterial concentrations were enumerated via microscopic counts of colony-forming units on agar plates, one, six and twelve months after application of the biocidal treatments. Cultivable species were further characterized by morphological taxonomic analysis (algae and fungi) and DNA analysis by sequencing of 16S rDNA gene (bacteria) and the ITS region plus the D1/D2 region of the 28S rDNA gene (fungi) before and after one-year treatment. None of the treatments led to overgrowth of bacteria or fungi, while benzalkonium chloride and water (used as control) treatments were the most effective in preventing bacterial recolonization and Biotin T® was the most effective in preventing fungal recolonization. Although the bacterial population did not increase in numbers after any of the treatments, the diversity was altered, with Bacillus halotolerans disappearing and Bacillus pumilus and Brachybacterium paraconglomeratum appearing in the areas treated with biocides. In fungi, Eutypa sp. was eliminated with all biocides except with Preventol RI80® and no species was promoted.

Effect of fungal, oomycete and nematode interactions on apple root development in replant soil

BackgroundApple replant disease (ARD) is a phenomenon associated with poor tree establishment at sites where the same, or a closely-related species, has grown for at least 1–2 years. No single organism has been identified as the universal causal agent, but there is increasing evidence that multiple soil-borne plant pathogenic fungi and oomycetes form an ARD disease complex. Root damage caused by root lesion nematodes has also been implicated in facilitating the entry of pathogens into root tissues resulting in the development of severe ARD.MethodsWe used a reductionist approach to determine effects of one or more members of the ARD complex on ARD in a number of selected rootstock genotypes with contrasting characteristics. Through a 15-month pot-based experiment in which semi-selective biocides were applied to soil from a replant orchard, we investigated (1) the nature of the interactions (i.e. antagonistic, additive or synergistic) between different groups of soil biota and ARD severity, and (2) whether rootstock characteristics modify ARD severity.ResultsThere might be competitive interactions between oomycetes and fungal pathogens in infecting apple roots and hence subsequent ARD development. Controlling all three ARD components (oomycetes, fungi, and nematodes) led to the best root development. However, these effects on root development were not manifested in the above-ground tree development 15 months after treatment. Specific soil biocide treatments against fungi and oomycetes led to large changes in soil microbial communities whereas the nematicide treatment led to least changes. In spite of the observed ARD, comparing rhizosphere microbial sequences among treatments failed to reveal candidate pathogens for ARD.ConclusionsCandidate ARD oomycetes and fungal pathogens are likely to engage in competitive interactions among themselves in infecting apple roots. Although soil amendments affected soil microbiota, such effects appear to be very unpredictable.

High osmotic stress initiates expansion and detachment of Thalassospira sp. biofilms in glass microchannels

Control of microbial activity and biofilm growth is an essential factor in a variety of medical and industrial applications. As microbial biofilms can protect cells within from physical or chemical threats, biocide treatments are often limited in their efficiency due to the low permeability of the biofilm. Therefore, finding new treatment options against biofilms remains an issue of high importance. We explored the option of using osmotic pressure to physically deform the biofilm matrix and increase detachment from a glass surface. Our model system is a single-species biofilm of Thalassospira sp. growing in a microfluidic set-up, enabling the observation of changes in biofilm volume and detachment rate. We observed that injection of a high salinity brine (NaCl) led to a reduction of biofilm volume (water efflux), and that subsequent injection of low salinity brine caused biofilm expansion (water influx). The differential osmotic pressure imposed on the biofilm was sufficient to weaken its adhesive strength to the glass surface, causing major detachment. The current approach has value as a method for cleaning glass microfluidic channels and other glass tubing or equipment clogged by biofilms, thus avoiding the use of harsh chemicals. As the basic physical principle of osmotic pressure initiating biofilm expansion and detachment is universal, our findings could be applied to other forms of biofilm growth.

Linoleic acid inhibits Pseudomonas aeruginosa biofilm formation by activating diffusible signal factor-mediated quorum sensing.

Bacterial biofilm formation causes serious problems in various fields of medical, clinical, and industrial settings. Antibiotics and biocide treatments are typical methods used to remove bacterial biofilms, but biofilms are difficult to remove effectively from surfaces due to their increased resistance. An alternative approach to treatment with antimicrobial agents is using biofilm inhibitors that regulate biofilm development without inhibiting bacterial growth. In the present study, we found that linoleic acid (LA), a plant unsaturated fatty acid, inhibits biofilm formation under static and continuous conditions without inhibiting the growth of Pseudomonas aeruginosa. LA also influenced the bacterial motility, extracellular polymeric substance production, and biofilm dispersion by decreasing the intracellular cyclic diguanylate concentration through increased phosphodiesterase activity. Furthermore, quantitative gene expression analysis demonstrated that LA induced the expression of genes associated with diffusible signaling factor-mediated quorum sensing that can inhibit or induce the dispersion of P. aeruginosa biofilms. These results suggest that LA is functionally and structurally similar to a P. aeruginosa diffusible signaling factor (cis-2-decenoic acid) and, in turn, act as an agonist molecule in biofilm dispersion.

Effects of Material Type on Biofilm Response to an Oxidising Biocide in a Laboratory-Scale Cooling Tower System

Biofilms in industrial cooling tower systems are an important problem. The importance of the surface material in the response to an oxidising biocide (chloramine T trihydrate) was substantiated in our study. Polyvinyl chloride (PVC) cooling tower fill material, stainless steel cooling tower construction material and glass surfaces were compared by evaluating the bacterial loads on materials before and after biocidal treatment. The greatest logarithmic decrease in bacterial load was recorded as &gt;3 log for glass after the first two months and for PVC after the second month. Actively respiring bacterial counts and adenosine triphosphate (ATP) measurements showed that there was no significant difference in the sensitivity of biofilm-associated cells to the biocide on the different surfaces. In addition, the effect of the biocidal treatment decreased with increasing biofilm age, regardless of the material.

Biological Risk for Hypogea: Shared Data from Etruscan Tombs in Italy and Ancient Tombs of the Baekje Dynasty in Republic of Korea

Biological growth represents one of the main threats for the conservation of subterranean cultural heritage. Knowledge of the conditions which favour the various taxonomic groups is important in delineating their control methods. Combining our experience regarding hypogea in Italy and the Republic of Korea, we aim to perform a critical review and comparison of the Biodeterioration Patterns (BPs) found, the materials used, and the conservative treatments applied. For this purpose, we focused on Etruscan tombs (Italy, 7th to 3th century BC) and the ancient tombs of the Baekje Dynasty (Republic of Korea, 6th to 7th centuries AD), most of which have been designated UNESCO World Heritage Sites, collecting original and bibliographic data as well as official documents. Results highlight the rich biodiversity of the bacterial and fungal species. Phototrophs were observed only in niches with sufficient light and the development of roots was also detected. Changes in humidity and temperature, the nature of the soil, nutrient accumulation, and vegetation above the hypogea along with human activities explain the different BPs. The effects of biocide treatments are also discussed, such as the emergence of dangerous fungal species. The shared data also enhance the role of overlaying tumuli and vegetation as well as protective barriers to reduce biological risk.

Assessment of different methods for the removal of biofilms and lichens on gravestones of the English Cemetery in Florence

The control of biodeterioration encompasses the operations undertaken to eliminate the biological growth and, possibly, to delay a new colonization. The current attitude is generally oriented toward its planned removal whenever it causes an objective damage and/or structural impairments to the substratum. The English Cemetery, located in the centre of Florence, offers interesting features for a research focused on the removal of biofilms and lichens growing on stone surfaces of some tombs. The study compared the efficacy of two methods based on physical approach (mechanical cleaning with a brush and microwave heating) with a chemical approach using biocide ROCIMA™ 103 to remove biofilms and lichens from each tombstone. The research, focusing on methodologies with low impact for the environment, tested the efficacy of an innovative portable system that produces localized microwave heating. Its great advantage lays on lack of the potential risks associated with the irreversible application of microbicides. The assessment of the treatments' efficacy was carried out monitoring the chlorophyll a fluorescence's parameters, informative on the vitality and stress responses of photosynthetic organisms. The long-term monitoring of the recolonization after the treatments was performed for five years. The mechanical cleaning eliminated the superficial layer of biofilms and lichens but not the cells within the stones. The biocide was efficient in killing the biological growth; almost no recolonization was observed after about five years. The innovative microwave treatment was effective on biofilms and lichens, eliminating also cells present in the bulk of the substrata, but recolonization was observed after 15 months. This suggests that, dopo treatment aggiungere virgola the microwave treatment should be performed more frequently than biocide treatments yet guaranteeing lower impact on the environment.

Sustainable environmental remediation approach for biocide removal from water medium: a model biosorption study using activated biological waste

Within the scope of sustainable environmental remediation approach, a biosorbent prepared from the waste of Zostera marina coastal plant with chemical activation was used to effectively remove malachite green as a common biocidal agent from water environment in this work. The biocide treatment ability of activated biosorbent was interpreted through the characterization, optimization, equilibrium, thermodynamic, and kinetic studies. The characterization research showed that the biosorbent has an uneven surface and various active groups for the retention of biocide molecules. Langmuir isotherm was found to be the most appropriate model for the experimental equilibrium data. The maximum monolayer biosorption capacity was obtained as 103.834 mg g−1 under the optimum conditions (time of 6 h, pH of 4, temperature of 25 °C, biosorbent amount of 10 mg, and biocide concentration of 15 mg L−1). The biosorption system was determined to be spontaneous and exothermic in thermodynamic aspect. The experimental kinetic data were best described by the pseudo-second-order model. All these results indicated that the activated biological residue could be used as an environmentally friendly and effective biosorbent for the biocide removal from water environment in a sustainable way.

Macrobiological Degradation of Esterified Wood with Sorbitol and Citric Acid

There is a need for new solutions in wood protection against marine wood borers and termites in Europe. A new solution could be the esterification of wood with sorbitol and citric acid (SCA) since these are inexpensive and readily available feedstock chemicals and have shown protective properties against fungal wood degradation in earlier studies and prevented macrobiological degradation, as shown in this study. Protection of wood products in the marine environment lacks available wood preservatives that are approved for marine applications. Termite infestation is opposed mainly by biocide treatments of wood. Several wood modification systems show high resistance against both marine borers and subterranean termites. However, the existing commercialized wood modification products are costly. Both macrobiological forms of degradation represent a great threat for most European wood species, which are rapidly and severely degraded if not properly treated. This study investigated esterified wood in standard field trials against marine wood borers, and against subterranean termites in laboratory trials in a no-choice and choice test. The treatment showed good resistance against wood borers in the marine environment after one season and against subterranean termites in the laboratory after eight weeks. The low termite survival rate (SR) in the no-choice test during the first week of testing indicates a mode of action that is incomparable to other wood modification treatments.

CHOSEN BIOCIDES AGAINST VIGNA UNGUICULATA (L) WALP

ABSTRACT Field trials were conducted with cowpea (Vamban 1) to evaluate some selected biocides the cowpea insects. Among the biocides, spray of neem seed kernel extract (NSKE) at 5% was effective in reducing the population of cowpea sucking insect, whitefly followed by azadirachtin at 1%. Spotted pod borer, M. vitrata incidence is less in the biocides treatments. Among the tested biocides, NSKE at 5% was effective in the management of spotted pod borer followed by azadirachtin at 1%. Cumulative pod damage by cowpea pod borers was minimum in indoxacarb at 0.7 mL/L treatment followed by NSKE at 5%. High cowpea seed yield was recorded in the treatment, indoxacarb at 0.7ml/litre followed by azadirachtin at 1%. In all the seasons, coccinellid beetles appeared in more numbers in the unsprayed plots followed by biocide treatments. In insecticide sprayed plots, comparatively this predatory beetle population was less. Number of spiders per 10 plants was more in the unsprayed plots. When insecticide and biocide treatments were compared, the biocide treatments harboured more spider population. Among the biocide treatments, in Beauveria bassiana at 10 gm/L sprayed plots, spiders were more followed by azadirachtin at 1%.

Nutrient Level Determines Biofilm Characteristics and Subsequent Impact on Microbial Corrosion and Biocide Effectiveness.

The impact that nutrient level has on biofilm characteristics, biocide effectiveness, and the associated risk of microbiologically influenced corrosion (MIC) was assessed using multispecies biofilms from two different oilfield consortia. A range of microbiological, microscopy, and corrosion methods demonstrated that the continuous flow of nutrients for the microbial growth resulted in higher activity, thickness, and robustness of the biofilms formed on carbon steel, which induced greater localized corrosion compared to biofilms formed under batch, nutrient-depleted conditions. Despite of the differences in biofilm characteristics, biofilms displayed comparable susceptibilities to glutaraldehyde biocide, with similar log10 reductions and percent reductions of microorganisms under both nutrient conditions. Nevertheless, nutrient replenishment impacted the effectiveness of the biocide in controlling microbial populations; a higher concentration of cells survived the biocide treatment in biofilms formed under a continuous flow of nutrients. Complementary DNA-/RNA-based amplicon sequencing and bioinformatics analysis were used to discriminate the active within the total populations in biofilms established at the different nutrient conditions and allowed the identification of the microbial species that remained active despite nutrient depletion and biocide treatment. Detection of persistent active microorganisms after exposure to glutaraldehyde, regardless of biofilm structure, suggested the presence of microorganisms less susceptible to this biocide and highlighted the importance of monitoring active microbial species for the early detection of biocide resistance in oil production facilities.IMPORTANCE Microbiologically influenced corrosion (MIC) is a complex process that generates economic losses to the industry every year. Corrosion must be managed to prevent a loss of containment of produced fluids to the external environment. MIC management includes the identification of assets with higher MIC risk, which could be influenced by nutrient levels in the system. Assessing biofilms under different nutrient conditions is essential for understanding the impact of flow regime on microbial communities and the subsequent impact on microbial corrosion and on the effectiveness of biocide treatment. This investigation simulates closely oil production systems, which contain piping sections exposed to continuous flow and sections that remain stagnant for long periods. Therefore, the results reported here are useful for MIC management and prevention. Moreover, the complementary methodological approach applied in this investigation highlighted the importance of implementing RNA-based methods for better identification of active microorganisms that survive stress conditions in oil systems.

Identification and Characterization of Potential Biocide-Resistant Fungal Strains from Infested Leathers

This study is aimed at identification of biocide tolerant/resistant fungal strains afflicting the leather industry. Fungal infestation occurs sometimes despite biocide treatment during leather processing. This persistent growth can be due to the development of biocide resistance which can lead to health hazards and economic loss. As no study has so far been reported to either confirm this or to identify such fungal strains, a systematic approach has been made in this study to address these aspects. Fungal strains were collected from infested leathers from tanneries to identify biocide resistant fungal strains afflicting leather industry. Phenotypic characterization revealed Aspergillus as the most dominant with 58% occurrence. Ten isolates were subjected to 18s rRNA sequencing and four strains were identified as Aspergillus niger. An in-vitro susceptibility to four leather fungicides was assessed to identify the biocide tolerant strains. S-6 A. niger strain was found to be the most tolerant as evidenced by high MIC (7.81µg ml-1) against the most effective biocide, 2-(thiocyanomethylthio) benzothiazole. In-vivo studies on chrome-tanned leathers also confirmed this finding. SEM studies revealed considerable morphological changes in S-6 compared to wild strain providing further evidence that it may have developed biocide resistance.

Photodegradation influences litter decomposition rate in a humid tropical ecosystem, Brazil

Solar radiation in general and UV radiation in particular have been recognized to stimulate plant litter decomposition through photochemical mineralization of organic molecules such as lignin and through facilitation of microbial decomposition in dryland ecosystems. However, little is known about how photodegradation may influence decomposition in other ecosystems not subject to moisture limitations and under what conditions photodegradation may be favored. Decomposition in humid tropical ecosystems is a complex process, and it can be influenced by a number of environmental factors that are distinct from arid and semi-arid ecosystems. To assess the mechanisms underlying photodegradation by ultraviolet B (UV-B) radiation in a humid tropical ecosystem, we designed a 300-day field experiment in a tropical site in Brazil with high levels of annual precipitation, compared to arid ecosystems, and exposed litter to three levels of radiation (full sun, UV-B removed, and shade) combined with a biocide treatment. Results show that after nearly one year of exposure, the microbial biomass was not affected by UV-B incidence, and this effect has not yet been fully understood for tropical ecosystems. Modeled using an exponential deceleration equation, the removal of UV-B radiation decelerated the plant litter decomposition rate for the control conditions by 21% compared to litter exposed to full sun. Interestingly, shaded litter exhibited similar mass loss compared to litter exposed to full sun. Furthermore, differences in the decay constant among radiation treatments due to the UV-B effect were independent of lignin loss. Overall, our study suggests that UV-B radiation contributed to plant litter decomposition through carbon losses but had no discernible effect on nitrogen, lignin, or cellulose loss specifically. Importantly, our results demonstrate that photodegradation occurs under humid tropical conditions, and further studies are necessary to examine the mechanisms of carbon loss.