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Summary Interest in understanding prokaryotic biotransformation of high‐molecular‐weight polycyclic aromatic hydrocarbons (HMW PAHs) has continued to grow and the scientific literature shows that studies in this field are originating from research groups from many different locations throughout the world. In the last 10 years, research in regard to HMW PAH biodegradation by bacteria has been further advanced through the documentation of new isolates that represent diverse bacterial types that have been isolated from different environments and that possess different metabolic capabilities. This has occurred in addition to the continuation of in‐depth comprehensive characterizations of previously isolated organisms, such as Mycobacterium vanbaalenii PYR‐1. New metabolites derived from prokaryotic biodegradation of four‐ and five‐ring PAHs have been characterized, our knowledge of the enzymes involved in these transformations has been advanced and HMW PAH biodegradation pathways have been further developed, expanded upon and refined. At the same time, investigation of prokaryotic consortia has furthered our understanding of the capabilities of microorganisms functioning as communities during HMW PAH biodegradation.

Understanding the biotransformation mechanisms of toxic sulfur-containing polycyclic aromatic hydrocarbon (PASH) pollutants such as benzothiophene (BT) is useful for predicting their environmental fates. In the natural environment, nondesulfurizing hydrocarbon-degrading bacteria are major active contributors to PASH biodegradation at petroleum-contaminated sites; however, BT biotransformation pathways by this group of bacteria are less explored when compared to desulfurizing organisms. When a model nondesulfurizing polycyclic aromatic hydrocarbon-degrading soil bacterium, Sphingobium barthaii KK22, was investigated for its ability to cometabolically biotransform BT by quantitative and qualitative methods, BT was depleted from culture media but was biotransformed into mostly high molar mass (HMM) hetero and homodimeric ortho-substituted diaryl disulfides (diaryl disulfanes). HMM diaryl disulfides have not been reported as biotransformation products of BT. Chemical structures were proposed for the diaryl disulfides by comprehensive mass spectrometry analyses of the chromatographically separated products and were supported by the identification of transient upstream BT biotransformation products, which included benzenethiols. Thiophenic acid products were also identified, and pathways that described BT biotransformation and novel HMM diaryl disulfide formation were constructed. This work shows that nondesulfurizing hydrocarbon-degrading organisms produce HMM diaryl disulfides from low molar mass polyaromatic sulfur heterocycles, and this may be taken into consideration when predicting the environmental fates of BT pollutants.

MytiLec; a novel lectin isolated from the Mediterranean mussel (Mytilus galloprovincialis); shows strong binding affinity to globotriose (Gb3: Galα1-4Galβ1-4Glc). MytiLec revealed β-trefoil folding as also found in the ricin B-subunit type (R-type) lectin family, although the amino acid sequences were quite different. Classification of R-type lectin family members therefore needs to be based on conformation as well as on primary structure. MytiLec specifically killed Burkitt's lymphoma Ramos cells, which express Gb3. Fluorescein-labeling assay revealed that MytiLec was incorporated inside the cells. MytiLec treatment of Ramos cells resulted in activation of both classical MAPK/ extracellular signal-regulated kinase and extracellular signal-regulated kinase (MEK-ERK) and stress-activated (p38 kinase and JNK) Mitogen-activated protein kinases (MAPK) pathways. In the cells, MytiLec treatment triggered expression of tumor necrosis factor (TNF)-α (a ligand of death receptor-dependent apoptosis) and activation of mitochondria-controlling caspase-9 (initiator caspase) and caspase-3 (activator caspase). Experiments using the specific MEK inhibitor U0126 showed that MytiLec-induced phosphorylation of the MEK-ERK pathway up-regulated expression of the cyclin-dependent kinase inhibitor p21, leading to cell cycle arrest and TNF-α production. Activation of caspase-3 by MytiLec appeared to be regulated by multiple different pathways. Our findings, taken together, indicate that the novel R-type lectin MytiLec initiates programmed cell death of Burkitt’s lymphoma cells through multiple pathways (MAPK cascade, death receptor signaling; caspase activation) based on interaction of the lectin with Gb3-containing glycosphingolipid-enriched microdomains on the cell surface.

3-Methylindole, also referred to as skatole, is a pollutant of environmental concern due to its persistence, mobility and potential health impacts. Petroleum refining, intensive livestock production and application of biosolids to agricultural lands result in releases of 3-methylindole to the environment. Even so, little is known about the aerobic biodegradation of 3-methylindole and comprehensive biotransformation pathways have not been established. Using glycerol as feedstock, the soil bacterium Cupriavidus sp. strain KK10 biodegraded 100 mg/L of 3-methylindole in 24 h. Cometabolic 3-methylindole biodegradation was confirmed by the identification of biotransformation products through liquid chromatography electrospray ionization tandem mass spectrometry analyses. In all, 14 3-methylindole biotransformation products were identified which revealed that biotransformation occurred through different pathways that included carbocyclic aromatic ring-fission of 3-methylindole to single-ring pyrrole carboxylic acids. This work provides first comprehensive evidence for the aerobic biotransformation mechanisms of 3-methylindole by a soil bacterium and expands our understanding of the biodegradative capabilities of members of the genus Cupriavidus towards heteroaromatic pollutants.

A specific galactose-binding lectin was shown to inhibit the hemolytic effect of streptolysin O (SLO), an exotoxin produced by Streptococcus pyogenes. Commercially available lectins that recognize N-acetyllactosamine (ECA), T-antigen (PNA), and Tn-antigen (ABA) agglutinated rabbit erythrocytes, but had no effect on SLO-induced hemolysis. In contrast, SLO-induced hemolysis was inhibited by AKL, a lectin purified from sea hare (Aplysia kurodai) eggs that recognizes α-galactoside oligosaccharides. This inhibitory effect was blocked by the co-presence of d-galactose, which binds to AKL. A possible explanation for these findings is that cholesterol-enriched microdomains containing glycosphingolipids in the erythrocyte membrane become occupied by tightly stacked lectin molecules, blocking the interaction between cholesterol and SLO that would otherwise result in penetration of the membrane. Growth of S. pyogenes was inhibited by lectins from a marine invertebrate (AKL) and a mushroom (ABA), but was promoted by a plant lectin (ECA). Both these inhibitory and promoting effects were blocked by co-presence of galactose in the culture medium. Our findings demonstrate the importance of glycans and lectins in regulating mechanisms of toxicity, creation of pores in the target cell membrane, and bacterial growth.

Summary A pathway for the biotransformation of the environmental pollutant and high‐molecular weight polycyclic aromatic hydrocarbon (PAH) benzo[k]fluoranthene by a soil bacterium was constructed through analyses of results from liquid chromatography negative electrospray ionization tandem mass spectrometry (LC/ESI(–)‐MS/MS). Exposure of Sphingobium sp. strain KK22 to benzo[k]fluoranthene resulted in transformation to four‐, three‐ and two‐aromatic ring products. The structurally similar four‐ and three‐ring non‐alternant PAHs fluoranthene and acenaphthylene were also biotransformed by strain KK22, and LC/ESI(–)‐MS/MS analyses of these products confirmed the lower biotransformation pathway proposed for benzo[k]fluoranthene. In all, seven products from benzo[k]fluoranthene and seven products from fluoranthene were revealed and included previously unreported products from both PAHs. Benzo[k]fluoranthene biotransformation proceeded through ortho‐cleavage of 8,9‐dihydroxy‐benzo[k]fluoranthene to 8‐carboxyfluoranthenyl‐9‐propenic acid and 9‐hydroxy‐fluoranthene‐8‐carboxylic acid, and was followed by meta‐cleavage to produce 3‐(2‐formylacenaphthylen‐1‐yl)‐2‐hydroxy‐prop‐2‐enoic acid. The fluoranthene pathway converged with the benzo[k]fluoranthene pathway through detection of the three‐ring product, 2‐formylacenaphthylene‐1‐carboxylic acid. Production of key downstream metabolites, 1,8‐naphthalic anhydride and 1‐naphthoic acid from benzo[k]fluoranthene, fluoranthene and acenaphthylene biotransformations provided evidence for a common pathway by strain KK22 for all three PAHs through acenaphthoquinone. Quantitative analysis of benzo[k]fluoranthene biotransformation by strain KK22 confirmed biodegradation. This is the first pathway proposed for the biotransformation of benzo[k]fluoranthene by a bacterium. Identification of products produced by a soil bacterium from the biotransformation of the 5‐ring PAH benzo[k]fluoranthene by using LC/ESI‐MS/MS techniques. Results from the biotransformation of 3‐ and 4‐ring structurally analogous PAHs by the same strain were used to confirm the biotransformation pathway proposed for benzo[k]fluoranthene.

The complex and diverse structural configurations of polycyclic aromatic hydrocarbons (PAHs), combined with their low bioavailability, hydrophobic nature, strong sorption phenomena, and high persistence in soil makes the design of effective bioremediation methodologies a challenge. The multi-phasic nature of the bioremediation process, restricted mass transfer and non-availability of degrading soil microflora further compound the problem. In this direction, this communication presents a focused review of bioremediation technologies used recently for the treatment of PAH-contaminated soils. The specific roles of important factors affecting bioremediation process efficiency are discussed. Finally some of the recently used strategies to enhance bioremediation process efficiency, including bioaugmentation, biostimulation, rhizoremediation, the use of chemotaxins, the biomimetic catalytic system approach, and integrated techniques, are reviewed.

The authors wish to make the following correction to their paper [1]. [...]

Toward the development of ecotoxicology methods to investigate microbial markers of impacts of hydrocarbon processing activities, DNA adductomic analyses were conducted on a sphingomonad soil bacterium. From growing cells that were exposed or unexposed to acrolein, a commonly used biocide in hydraulic fracturing processes, DNA was extracted, digested to 2′‐deoxynucleosides and analyzed by liquid chromatography‐positive ionization electrospray‐tandem mass spectrometry in selected reaction monitoring mode transmitting the [M + H]+ > [M + H − 116]+ transition over 100 transitions. Overall data shown as DNA adductome maps revealed numerous putative DNA adducts under both conditions with some occurring specifically for each condition. Adductomic analyses of triplicate samples indicated that elevated levels of some targeted putative adducts occurred in exposed cells. Two exposure‐specific adducts were identified in exposed cells as 3‐(2′‐deoxyribosyl)‐5,6,7,8‐tetrahydro‐6‐hydroxy‐(and 8‐hydroxy‐)pyrimido[1,2‐a]‐ purine‐(3H)‐one (6‐ and 8‐hydroxy‐PdG) following synthesis of authentic standards of these compounds and subsequent analyses. A time course experiment showed that 6‐ and 8‐hydroxy‐PdG were detected in bacterial DNA within 30 min of acrolein exposure but were not detected in unexposed cells. This work demonstrated the first application of DNA adductomics to examine DNA damage in a bacterium and sets a foundation for future work. DNA adductomic analyses were conducted on a sphingomonad soil bacterium to investigate potential DNA damage markers. DNA adducts that were specific to exposure conditions were identified. This is the first application of DNA adductomics to a prokaryotic organism.

A divalent cation-independent lectin—HOL-18, with cytotoxic activity against leukemia cells, was purified from a demosponge, Halichondria okadai. HOL-18 is a 72 kDa tetrameric lectin that consists of four non-covalently bonded 18 kDa subunits. Hemagglutination activity of the lectin was strongly inhibited by chitotriose (GlcNAcβ1-4GlcNAcβ1-4GlcNAc), fetuin and mucins from porcine stomach and bovine submaxillary gland. Lectin activity was stable at pH 4–12 and temperatures lower than 60 °C. Frontal affinity chromatography with 16 types of pyridylaminated oligosaccharides indicated that the lectin had an affinity for N-linked complex-type and sphingolipid-type oligosaccharides with N-acetylated hexosamines and neuramic acid at the non-reducing termini. The lectin killed Jurkat leukemia T cells and K562 erythroleukemia cells in a dose- and carbohydrate-dependent manner.