Tuning in to multiple predators: conflicting demands for shell morphology in a freshwater snail

1. We examined the response to chemical cues from fish and crayfish, two predators with contrasting feeding modes, and their single and combined effect on shell morphology in the freshwater snail Radix balthica. 2. Snails were subjected to four treatments: tench (Tinca tinca), signal crayfish (Pacifastacus leniusculus), a combination of tench and signal crayfish and no predators (control). Shell shape, crushing resistance and shell thickness were quantified. We also analysed whether shape or shell thickness contributes most to crushing resistance. 3. Chemical cues from the fish induced a rounder shell shape in R. balthica, a thicker shell and a higher crushing resistance, whereas crayfish chemical cues had no effect on shell morphology, shell thickness or crushing resistance. Shell shape contributed more to crushing resistance than shell thickness. 4. The combined predator treatment showed an intermediate response between the fish and crayfish treatments. Shell roundness was reduced compared with the fish treatment, but the reduced crushing resistance that comes with a less rounded shell was compensated by an increased investment in extra shell material, exceeding that of the fish treatment. 5. Our study extends previous studies of multipredator effects on phenotypically plastic freshwater snails by showing that the snails are able to fine‐tune different elements of morphology to counter predator‐specific foraging modes.     

Role of PII proteins in nitrogen fixation control of Herbaspirillum seropedicae strain SmR1

Background  

The PII protein family comprises homotrimeric proteins which act as transducers of the cellular nitrogen and carbon status in prokaryotes and plants. In Herbaspirillum seropedicae, two PII-like proteins (GlnB and GlnK), encoded by the genes glnB and glnK, were identified. The glnB gene is monocistronic and its expression is constitutive, while glnK is located in the nlmAglnKamtB operon and is expressed under nitrogen-limiting conditions.     

Patterns of cervical metastasis from carcinoma of the oral tongue

Background  

Cancer of the oral tongue is the second most common cancer among males in various parts of India. Despite advances in diagnosis and treatment the failure rates in cancer of the oral tongue are high and survival poor. Majority of these failures occur in untreated neck.     

Nitrogen export from a watershed subjected to partial salvage logging

Logging has been shown to induce nitrogen (N) leaching. We hypothesized that logging a watershed that previously exhibited forest decline symptoms would place additional stress on the ecosystem and result in greater N loss, compared to harvesting vigorous forests. We conducted a 10-year (1988 to 1998) assessment of N export from the Baldwin Creek watershed in southwestern Pennsylvania that was partially clearcut to salvage dead and dying northern red oak. N export from the watershed increased significantly following salvage logging operations and did not completely return to prelogging levels by the end of the study period. The largest annual NO3-N export of 13 kg/ha was observed during the first year after harvesting, an increase of approximately 10 kg/ha. Compared to data from other Appalachian Mountain watersheds in North Carolina, West Virginia, and Pennsylvania, calculated N loss for Baldwin Creek was considerably greater. Longer periods of reduced N uptake due to slow revegetation of salvage logged areas, coupled with increased amounts of N available to leaching, could have accounted for the large N losses observed for Baldwin Creek. Salvage logging of dead and dying trees from forested watersheds in this region appears to have the potential to result in much larger N losses than previously reported for harvest of healthy stands.     

Diet of bluegill Lepomis macrochirus in a South African reservoir during winter and summer

Alien fishes are considered a major threat to aquatic biodiversity in South Africa, yet relatively little regional information on their biology and ecology is available for many of these species. Seasonal changes in the diet of the bluegill Lepomis macrochirus in Howieson’s Poort Dam, Grahamstown, were assessed during summer and winter in 2014–2015, using stomach content analysis. In winter, juvenile and adult fish diets were dominated by crustacean zooplankton and insects, respectively. In summer, juvenile fish fed on crustaceans and insects, whereas adults consumed mostly fish eggs, indicating a potential impact by these invasive fish on native fish through oophagy.     

Molecular phylogenetic and biogeochemical studies of sulfate-reducing bacteria in the rhizosphere of spartina alterniflora

The population composition and biogeochemistry of sulfate-reducing bacteria (SRB) in the rhizosphere of the marsh grass Spartina alterniflora was investigated over two growing seasons by molecular probing, enumerations of culturable SRB, and measurements of SO42- reduction rates and geochemical parameters. SO42- reduction was rapid in marsh sediments with rates up to 3.5 &mgr;mol ml-1 day-1. Rates increased greatly when plant growth began in April and decreased again when plants flowered in late July. Results with nucleic acid probes revealed that SRB rRNA accounted for up to 43% of the rRNA from members of the domain Bacteria in marsh sediments, with the highest percentages occurring in bacteria physically associated with root surfaces. The relative abundance (RA) of SRB rRNA in whole-sediment samples compared to that of Bacteria rRNA did not vary greatly throughout the year, despite large temporal changes in SO42- reduction activity. However, the RA of root-associated SRB did increase from <10 to >30% when plants were actively growing. rRNA from members of the family Desulfobacteriaceae comprised the majority of the SRB rRNA at 3 to 34% of Bacteria rRNA, with Desulfobulbus spp. accounting for 1 to 16%. The RA of Desulfovibrio rRNA generally comprised from <1 to 3% of the Bacteria rRNA. The highest Desulfobacteriaceae RA in whole sediments was 26% and was found in the deepest sediment samples (6 to 8 cm). Culturable SRB abundance, determined by most-probable-number analyses, was high at >10(7) ml-1. Ethanol utilizers were most abundant, followed by acetate utilizers. The high numbers of culturable SRB and the high RA of SRB rRNA compared to that of Bacteria rRNA may be due to the release of SRB substrates in plant root exudates, creating a microbial food web that circumvents fermentation.     

Codon use and the rate of divergence of land plant chloroplast genes

Codon fitnesses for chloroplast genes were estimated using the relative synonymous codon use of psbA, which has a different pattern of codon use than other chloroplast genes and is the major translation product of the chloroplast. These estimates were used to calculate the codon adaptation index (CAI) of chloroplast genes from Marchantia polymorpha, Nicotiana tabacum, and Chlamydomonas reinhardtii. The genes with the highest CAI values in M. polymorpha correspond to those that are expressed at the highest levels. The rate of divergence between M. polymorpha and both C. reinhardtii and N. tabacum is inversely related to the CAI value of the M. polymorpha gene. The data suggest that selection is acting on the synonymous codon use of the highly expressed genes of the M. polymorpha chloroplast genome. The data set is inconclusive about N. tabacum genes, but, as there is a weaker correspondence between CAI value and expression level, it suggests that selection is not operating in this lineage.      

Purification and characterization of maltooligosaccharide-forming amylase from Bacillus circulans GRS 313

A maltooligosaccharide-forming amylase that hydrolyzes starch into maltotriose and maltopentaose was found in the culture filtrate of a strain of Bacillus circulans GRS 313 isolated from local soil. The enzyme was purified by organic solvent fractionation, Sephadex G-100 gel filtration and CM-Sephadex column chromatography. Optimum pH and temperature of amylase were evaluated using response surface methodology (RSM) and were found to be 48°C and 4.9, respectively. The enzyme was stable up to 60°C and its pH stability was in the range of 5.0–8.0. The K _m and V _max of the amylase with starch were 11.66 mg/ml and 68.97 U, respectively, and the energy of activation, E _a, was 7.52 kcal/mol. Dextrin inhibited the enzyme competitively, with a K _i of 6.1 mg/ml, and glucose caused noncompetitive inhibition with a K _i of 9.5 mg/ml. The enzyme was inhibited by Hg²⁺, Mn²⁺, Fe³⁺ and Cu²⁺ and enhanced by Co²⁺ and Mg²⁺. EDTA reversed the inhibitory effect of the metals. Paper chromatographic and high-performance liquid chromatography analysis of the products of the amylolytic reaction showed the presence of maltotriose, maltotetraose, maltopentaose, maltose and glucose in the starch hydrolysate. Journal of Industrial Microbiology & Biotechnology (2002) 28, 193–200 DOI: 10.1038/sj/jim/7000220 Received 11 December 2000/ Accepted in revised form 22 October 2001