Thermostable dextranases: screening, detection and preliminary characterization

Screening methods have been developed for detection of micro-organisms producing thermostable dextranases. They utilize the incorporation of Blue Dextran into agar or liquid culture media for isolation of active dextranase producers growing at temperatures above 55°C. A variety of high temperature environments in sugar factories and naturally occurring thermal water samples were excellent sources of dextranase producers. A number of aerobic and anaerobic thermophilic bacteria, isolated from these sources, were found to produce thermostable dextranases. Dextranases with the greatest thermostability were found in cultures of anaerobic bacteria grown above 65°C. Temperature optima were determined for several crude enzyme preparations, four of which exhibited temperature optima in the range 65–85°C.     

Extraordinary Conservation of Cysteines Among Homologous Chironomus Silk Proteins sp185 and sp220

Aquatic larvae of the midge, Chironomus tentans, synthesize a 185-kDa silk protein (sp185) with the cysteine-containing motif Cys-X-Cys-X-Cys (where X is any residue) every 20–28 residues. We report here the cloning and full-length sequence of cDNAs encoding homologous silk proteins from Chironomus pallidivittatus (sp185) and Chironomus thummi (sp220). Deduced amino acid sequences reveal proteins of nearly identical mass composed of 72 blocks of 20–28 residues, 61% of which can be described by the motif X_5–8-Cys-X₅-(Trp/Phe/Tyr)-X₄-Cys-X-Cys-X-Cys. Spatial arrangement of these residues is preserved more than surrounding sequences. cDNA clones enabled us to map the genes on polytene chromosomes and identify for the first time the homolog of the Camptochironomus Balbiani ring 3 locus in Chironomus thummi. The apparent molecular weight difference between these proteins (185 vs 220 kDa) is not attributable to primary structure and may be due to differential N-linked glycosylation. DNA distances and codon substitutions indicate that the C. tentans and C. pallidivittatus genes are more related to each other than either is to C. thummi; however, substitution rates for the 5′- and 3′-halves of these genes are different. Blockwise sequence comparisons suggest intragenic variation in that some regions evolved slower or faster than the mean and may have been subjected to different selective pressures. Received: 30 August 1996 / Accepted: 6 November 1996     

Fe(III) as an electron acceptor for H2 oxidation in thermophilic anaerobic enrichment cultures from geothermal areas

Six sustainable enrichment cultures of thermophilic H₂-oxidizing microorganisms utilizing Fe(III) as an electron acceptor were obtained from geothermally heated environments located on two continents (America, Eurasia) and on islands in the Northern (Iceland) and Southern (Fiji) hemispheres, demonstrating the wide distribution of these microorganisms. The main products of amorphic Fe(III) oxide reduction were magnetite and siderite. The observed temperature range for Fe(III) reduction in growing cultures was from 55°C to 87°C, extending the known limits for growth of Fe(III)-reducing microorganisms producing extracellular magnetite to nearly 90°C. Received: August 13, 1996 / Accepted: January 17, 1997     

TC21 causes transformation by Raf-independent signaling pathways.

Although the Ras-related protein TC21/R-Ras2 has only 55% amino acid identity with Ras proteins, mutated forms of TC21 exhibit the same potent transforming activity as constitutively activated forms of Ras. Therefore, like Ras, TC21 may activate signaling pathways that control normal cell growth and differentiation. To address this possibility, we determined if regulators and effectors of Ras are also important for controlling TC21 activity. First, we determined that Ras guanine nucleotide exchange factors (SOS1 and RasGRF/CDC25) synergistically enhanced wild-type TC21 activity in vivo and that Ras GTPase-activating proteins (GAPs; p120-GAP and NF1-GAP) stimulated wild-type TC21 GTP hydrolysis in vitro. Thus, extracellular signals that activate Ras via SOS1 activation may cause coordinate activation of Ras and TC21. Second, we determined if Raf kinases were effectors for TC21 transformation. Unexpectedly, yeast two-hybrid binding analyses showed that although both Ras and TC21 could interact with the isolated Ras-binding domain of Raf-1, only Ras interacted with full-length Raf-1, A-Raf, or B-Raf. Consistent with this observation, we found that Ras- but not TC21-transformed NIH 3T3 cells possessed constitutively elevated Raf-1 and B-Raf kinase activity. Thus, Raf kinases are effectors for Ras, but not TC21, signaling and transformation. We conclude that common upstream signals cause activation of Ras and TC21, but activated TC21 controls cell growth via distinct Raf-independent downstream signaling pathways.     

The Rap and Hor proteins of Erwinia, Serratia and Yersinia: a novel subgroup in a growing superfamily of proteins regulating diverse physiological processes in bacterial pathogens

The enteric bacterium Serratia marcescens is an opportunistic human pathogen. The strain ATCC39006 makes the red pigment, prodigiosin (Pig), and the β-lactam antibiotic carbapenem (Car). Mutants were isolated that were concomitantly defective for Pig and Car production. These mutants were found to have a mutation in the rap gene (regulation of antibiotic and pigment). Sequence analysis of the rap gene revealed a predicted protein product showing strong homology to SlyA, originally thought to be a haemolytic virulence determinant in Salmonella typhimurium. Homologues of rap were detected in several bacterial genera, including Salmonella, Yersinia, Enterobacter , and species of the plant pathogen, Erwinia. The Erwinia hor_Er (homologue of rap ) and the Yersinia hor_Ye genes were also found to be very similar to rap and slyA. Marker exchange mutagenesis of hor_Er revealed that it encoded a regulatory protein controlling the production of antibiotic and exoenzyme virulence determinants in the phytopathogen, Erwinia carotovora subspecies carotovora. We have shown that these new homologues of SlyA form a highly conserved subgroup of a growing superfamily of bacterial regulatory proteins controlling diverse physiological processes in human, animal and plant pathogens.     

Growth,ethanol production,and inulinase activity on various inulin substrates by mutant <Emphasis Type="Italic">Kluyveromyces marxianus</Emphasis> strains NRRL Y-50798 and NRRL Y-50799

Economically important plants contain large amounts of inulin. Disposal of waste resulting from their processing presents environmental issues. Finding microorganisms capable of converting inulin waste to biofuel and valuable co-products at the processing site would have significant economic and environmental impact. We evaluated the ability of two mutant strains of Kluyveromyces marxianus (Km7 and Km8) to utilize inulin for ethanol production. In glucose medium, both strains consumed all glucose and produced 0.40 g ethanol/g glucose at 24 h. In inulin medium, Km7 exhibited maximum colony forming units (CFU)/mL and produced 0.35 g ethanol/g inulin at 24 h, while Km8 showed maximum CFU/mL and produced 0.02 g ethanol/g inulin at 96 h. At 24 h in inulin + glucose medium, Km7 produced 0.40 g ethanol/g (inulin + glucose) and Km8 produced 0.20 g ethanol/g (inulin + glucose) with maximum CFU/mL for Km8 at 72 h, 40 % of that for Km7 at 36 h. Extracellular inulinase activity at 6 h for both Km7 and Km8 was 3.7 International Units (IU)/mL.     

GPS tracking reveals rafting behaviour of Northern Gannets (Morus bassanus): implications for foraging ecology and conservation

Capsule Three quarters of tracked Northern Gannets (Morus bassanus) at Grassholm gathered in rafts around the colony, concentrated within a recently designated at-sea Special Protection Area (SPA), but rafting was not correlated with foraging effort.

Aims To investigate the incidence, distribution and foraging implications of Northern Gannet rafting behaviour in waters adjacent to a large colony.

Methods Using bird-borne global positioning system (GPS) loggers we reconstructed at-sea movement and used a speed filter to identify rafting behaviour within 10?km of the colony. We mapped the spatial distribution of rafting events from 160 breeding individuals over 5 years, and investigated the relationship between foraging effort (trip duration and total distance travelled) and the presence/absence of rafting.

Results On average, 74% of tracked birds engaged in rafting. Of the 381 foraging trips analysed, rafting was recorded on 237 (62%). Birds were more likely to raft on outbound (224 trips, 59%), than inbound journeys (38 trips, 10%). Presence/absence of rafting did not correlate significantly with foraging trip distance or duration nor with duration of nest attendance. The majority of rafting was concentrated in a 2-km radius around the colony within a recently designated seaward SPA extension. Birds showed low individual repeatability in rafting, although there was lower variation within, than among, individuals.

Conclusion Our results show that rafting is important for breeding gannets on Grassholm, and a recently designated at-sea SPA encapsulates the core distribution of rafting. Rafting did not appear to be correlated with foraging behaviour. Given the dearth of literature on rafting and the wealth of GPS tracking data for seabirds, we suggest that similar research be conducted elsewhere to further elucidate the ecological and applied significance of this behaviour.     

Collaborative research partnerships inform monitoring and management of aquatic ecosystems by Indigenous rangers

Aquatic ecosystems are critical to the long-term viability and vibrancy of communities and economies across northern Australia. In a region that supports significant cultural and ecological water values, partnerships between Indigenous and non-Indigenous stakeholders can benefit aquatic ecosystem management. We present, as a case study from the Kimberley region of Western Australia, a collaborative research program that successfully documented Indigenous and Western Scientific knowledge of remote wetlands, using a variety of field-based activities, questionnaires, interviews and workshops. The sharing of knowledge between Indigenous and non-Indigenous research partners facilitated a comprehensive understanding of ecosystem values, threats, processes, management priorities and aspirations. These formed the basis of a management plan and monitoring tools, designed to build the capacity of an Indigenous ranger group to engage in research, monitoring and management of wetlands. The project provides a useful example of the benefits of collaborations in the context of remote-area management where local communities are responsible for environmental management and monitoring, such as is the case in northern Australia and presumably other areas of the world.