Consequences of detritus type in an aquatic microsystem: effects on water quality, micro-organisms and performance of the dominant consumer

1. Variation in detritus quality and quantity can have significant effects on aquatic invertebrate food webs. Allochthonous inputs of detritus are the principal energy source for organisms in aquatic tree hole microsystems. We compared the effects of two major detritus types found in tree holes, senescent leaves (Sugar Maple and White Oak) and invertebrate carcasses (dead adult fruit flies and crickets), on several water quality characteristics of laboratory microcosms as well as on mass, survival and population performance of the dominant tree hole consumer, Ochlerotatus triseriatus (Diptera: Culicidae). To date, no study has documented the effects of animal detritus in tree hole microsystems or on resident consumers.2. Aquatic environments receiving invertebrate carcasses had significantly greater total nitrogen, total reactive phosphorus and higher pH, than leaf-based environments. Decay rate of invertebrate carcasses was greater compared to leaf material. Consumption of O(2) by micro-organisms increased with increasing detritus amounts, but we detected no difference between detritus types.3. Ochlerotatus triseriatus larvae grew faster in animal-based treatments, and mean mass of larvae was significantly greater when more animal detritus was used. The effect of animal-based treatments on larvae translated into higher performance for adults, which were three times heavier than counterparts from plant-based containers. Survivorship and estimated population growth rates were significantly greater for O. triseriatus reared on animal-based versus plant-based detritus.4. We hypothesise two mechanisms for the pronounced effect of invertebrate carcasses on mosquito performance relative to that associated with leaf detritus: (i) invertebrate carcasses decompose more quickly and release nutrients more effectively into the aquatic environment; or (ii) O. triseriatus larvae may directly ingest nutrient-rich components of invertebrate carcasses. Because even relatively small animal detritus additions can have strong effects on O. triseriatus populations, studies need to be conducted to explore the overall role of animal detritus in tree holes in nature.     

滴水湖沉积物中可培养优势微生物种群初探

于滴水湖湖心采集底泥样品,对底泥中可培养优势菌种进行分离、纯化,并利用Biolog微生物自动分析系统进行鉴定。结果显示,滴水湖沉积物中菌落总数为2.43×104CFU/g,分离纯化后的8株优势菌种中,革兰氏阴性菌占87.5%,其中7株为GN-NENT(革兰氏阴性非肠道菌)、1株为GP-ROD SB(革兰氏阳性芽孢杆菌)。鉴定结果显示,8株菌种分别为:鳗鱼气单孢菌(Aeromonas encheleia)、乙酸钙不动杆菌/基因型1(Acinetobacter calcoaceticus/genospecies1)、舒氏气单胞菌(Aeromonas schubertiiDNA group12)、腐败希瓦氏菌B(Shewanella putrefaciens B)、维罗纳/温和气单胞菌(Aeromonas veronii/sobria DNA group8)、坎氏弧菌(Vibrio campbelli)、蕈状芽孢杆菌(Bacillus mycoides)和梅氏弧菌(Vibrio metschnikovii)。     

Plastid DNA in the nucleus: New genes for old

Nuclear genomes of eukaryotes are bombarded by a continuous deluge of organellar DNA which contributes significantly to eukaryote evolution. Here, we present a new PCR-based method that allows the specific amplification of nuclear integrants of organellar DNA (norgs) by exploiting recent deletions present in organellar genome sequences. We have used this method to amplify nuclear integrants of plastid DNA (nupts) from the nuclear genomes of several nicotiana species and to study the evolutionary forces acting upon these sequences. The role of nupts in endosymbiotic evolution and the different genetic factors influencing the time available for a chloroplastic gene to be functionally relocated in the nucleus are discussed.     

Hypothesis: Gene‐rich plastid genomes in red algae may be an outcome of nuclear genome reduction

Red algae (Rhodophyta) putatively diverged from the eukaryote tree of life >1.2 billion years ago and are the source of plastids in the ecologically important diatoms, haptophytes, and dinoflagellates. In general, red algae contain the largest plastid gene inventory among all such organelles derived from primary, secondary, or additional rounds of endosymbiosis. In contrast, their nuclear gene inventory is reduced when compared to their putative sister lineage, the Viridiplantae, and other photosynthetic lineages. The latter is thought to have resulted from a phase of genome reduction that occurred in the stem lineage of Rhodophyta. A recent comparative analysis of a taxonomically broad collection of red algal and Viridiplantae plastid genomes demonstrates that the red algal ancestor encoded ~1.5× more plastid genes than Viridiplantae. This difference is primarily explained by more extensive endosymbiotic gene transfer (EGT) in the stem lineage of Viridiplantae, when compared to red algae. We postulate that limited EGT in Rhodophytes resulted from the countervailing force of ancient, and likely recurrent, nuclear genome reduction. In other words, the propensity for nuclear gene loss led to the retention of red algal plastid genes that would otherwise have undergone intracellular gene transfer to the nucleus. This hypothesis recognizes the primacy of nuclear genome evolution over that of plastids, which have no inherent control of their gene inventory and can change dramatically (e.g., secondarily non‐photosynthetic eukaryotes, dinoflagellates) in response to selection acting on the host lineage.     

Novel cytochromes P450 applications arising from the directed-evolution of recombinant micro-organisms

AIMS: Directed (forced) evolution of cytochromes P450 (overall 2700 CYP isoforms in non-recombinant biota) is a method that has been investigated in yeasts (and other micro-organisms) by aerobically growing brewers' yeast Saccharomyces cerevisiae in very high glucose (20%) media. METHODS AND RESULTS: Mitochondrial repression subverts cytochrome oxidase biosynthesis into manifest cytochromes P450 accumulation in brewers' yeast. A similar phenomenon is observed with the acridine-induced petit mutant. Cytochromes P450 EC 1.14.14.1 (and mimics) display a range of redox iron-mediated bioconversions in food processing, with mixed function oxidase (O2:mono-oxygenase) intervention results. Unfortunately these enzymes generate reactive oxygen species (ROS) through redox electron recycling, whilst isoform CYP 1A1 can activate precarcinogens such as benzo(a)pyrene to the ultimate (proximate) carcinogen that binds to nuclear DNA. CONCLUSIONS: In conclusion, another 5000 CYP isoforms, for example, might be identified in micro-organisms and many more made to order through recombinant DNA technology and utilized both in vitro and in vivo for aimed bioconversions in industry and in the environment, as part of the impact of greener-approach supporting strategies to minimize global pollution.