A comparative analysis reveals weak relationships between ecological factors and beta diversity of stream insect metacommunities at two spatial levels

The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted by insect group, latitude, spatial extent, altitudinal range, and dataset properties across multiple drainage basins throughout the world. Second, we assessed the relative roles of environmental and spatial factors in driving variation in assemblage composition within each drainage basin. Our analyses were based on a dataset of 95 stream insect metacommunities from 31 drainage basins distributed around the world. We used dissimilarity‐based indices to quantify beta diversity for each metacommunity and, subsequently, regressed beta diversity on insect group, latitude, spatial extent, altitudinal range, and dataset properties (e.g., number of sites and percentage of presences). Within each metacommunity, we used a combination of spatial eigenfunction analyses and partial redundancy analysis to partition variation in assemblage structure into environmental, shared, spatial, and unexplained fractions. We found that dataset properties were more important predictors of beta diversity than ecological and geographical factors across multiple drainage basins. In the within‐basin analyses, environmental and spatial variables were generally poor predictors of variation in assemblage composition. Our results revealed deviation from general biodiversity patterns because beta diversity did not show the expected decreasing trend with latitude. Our results also call for reconsideration of just how predictable stream assemblages are along ecological gradients, with implications for environmental assessment and conservation decisions. Our findings may also be applicable to other dynamic systems where predictability is low.     

Growth and arginine metabolism of the wine lactic acid bacteria Lactobacillus buchneri and Oenococcus oeni at different pH values and arginine concentrations

During malolactic fermentation (MLF) in grape must and wine, heterofermentative lactic acid bacteria may degrade arginine, leading to the formation of ammonia and citrulline, among other substances. This is of concern because ammonia increases the pH and thus the risk of growth by spoilage bacteria, and citrulline is a precursor to the formation of carcinogenic ethyl carbamate (EC). Arginine metabolism and growth of Lactobacillus buchneri CUC-3 and Oenococcus oeni strains MCW and Lo111 in wine were investigated. In contrast to L. buchneri CUC-3, both oenococci required a higher minimum pH for arginine degradation, and arginine utilization was delayed relative to the degradation of malic acid, the main aim of MLF. This allows the control of pH increase and citrulline formation from arginine metabolism by carrying out MLF with pure oenococcal cultures and inhibiting cell metabolism after malic acid depletion. MLF by arginine-degrading lactobacilli should be discouraged because arginine degradation may lead to the enhanced formation of acids from sugar degradation. A linear relationship was found between arginine degradation and citrulline excretion rates. From this data, strain-specific arginine-to-citrulline conversion ratios were calculated that ranged between 2.2 and 3.9% (wt/wt), and these ratios can be used to estimate the contribution of citrulline to the EC precursor pool from a given amount of initial arginine. Increasing arginine concentrations led to higher rates of growth of L. buchneri CUC-3 but did not increase the growth yield of either oenococcus. These results suggest the use of non-arginine-degrading oenococci for inducing MLF.     

Intracellular glucose 6-phosphate content in Streptomyces coelicolor upon environmental changes in a defined medium

A new, chemically defined medium providing dispersed growth and high biomass formation and a method for quantitative extraction of intracellular metabolites was used to investigate the cellular response of Streptomyces coelicolor A3(2) during growth and upon changes in nutrient utilization. Fast changes of the glucose 6-phosphate content precisely signaled transitions in the flow of carbon sources. The results indicate that intracellular pool sizes may be used to detect early nutrient limitations in view of the onset of antibiotic production. Additionally the results disclose characteristics of the regulation of maltose and glutamic acid uptake and degradation in S. coelicolor A3(2).     

Secreted Aspartic Protease Cleavage of Candida albicans Msb2 Activates Cek1 MAPK Signaling Affecting Biofilm Formation and Oropharyngeal Candidiasis

Perception of external stimuli and generation of an appropriate response are crucial for host colonization by pathogens. In pathogenic fungi, mitogen activated protein kinase (MAPK) pathways regulate dimorphism, biofilm/mat formation, and virulence. Signaling mucins, characterized by a heavily glycosylated extracellular domain, a transmembrane domain, and a small cytoplasmic domain, are known to regulate various signaling pathways. In Candida albicans, the mucin Msb2 regulates the Cek1 MAPK pathway. We show here that Msb2 is localized to the yeast cell wall and is further enriched on hyphal surfaces. A msb2Δ/Δ strain formed normal hyphae but had biofilm defects. Cek1 (but not Mkc1) phosphorylation was absent in the msb2Δ/Δ mutant. The extracellular domain of Msb2 was shed in cells exposed to elevated temperature and carbon source limitation, concomitant with germination and Cek1 phosphorylation. Msb2 shedding occurred differentially in cells grown planktonically or on solid surfaces in the presence of cell wall and osmotic stressors. We further show that Msb2 shedding and Cek1 phosphorylation were inhibited by addition of Pepstatin A (PA), a selective inhibitor of aspartic proteases (Saps). Analysis of combinations of Sap protease mutants identified a sap8Δ/Δ mutant with reduced MAPK signaling along with defects in biofilm formation, thereby suggesting that Sap8 potentially serves as a major regulator of Msb2 processing. We further show that loss of either Msb2 (msb2Δ/Δ) or Sap8 (sap8Δ/Δ) resulted in higher C. albicans surface β-glucan exposure and msb2Δ/Δ showed attenuated virulence in a murine model of oral candidiasis. Thus, Sap-mediated proteolytic cleavage of Msb2 is required for activation of the Cek1 MAPK pathway in response to environmental cues including those that induce germination. Inhibition of Msb2 processing at the level of Saps may provide a means of attenuating MAPK signaling and reducing C. albicans virulence.     

Orcein staining and the study of the effect of chemicals on chromosomes

Summary Plant materials of both dicotyledonous and monocotyledonous groups were subjected to treatment with alloxan followed by coumarin, phenols, oxyquinoline etc. for 3 to 4 hours.Root tips were then heated in an orcein-acid mixture for 10 to 40 seconds and studied after mounting in 1% orcein. Clear metaphase plates were obtained after 10 seconds of heating, whereas after 20 and 30 seconds considerable erosion and fragmentation respectively were recorded. Complete loss of stainability resulted after heating for 40 seconds.Fragmentation is caused only by orcein under heat conditions. This is demonstrated by control series checking all variables.Pretreatment with the chemicals stated is of absolute necessity for fragmentation. It is suggested that this pretreatment causes depolymerisation of DNA and lability of nucleoprotein linkage at certain segments from which the DNA becomes detached during subsequent heating.Of all the chemicals tested for pretreatment effects, marked positive results were obtained with alloxan (1 hour) followed by coumarin (2 hours at 16–20 ° C.). Phenols also gave positive results. The other chemicals tried need slightly longer time of treatment for fragment induction.     

Bonding, postpartum dysphoria, and social ties

Since the late 1970s, disruptions and “failure” of maternal-infant bonding have been causally linked to postpartum depression. Part I of this paper examines the grounds for this connection while tracing the ramifications of bonding theory (Klaus and Kennell 1976) through obstetrics, pediatrics, and psychiatry, as well as in the (mis)representations of it in the popular media. This discussion resolves into a view of maternal attachment as a long-term development progressively established through intensive mother-infant interaction. The forms of this interaction are phylogenetically determined, albeit culturally and personally mediated. Flowing from this premise, Part II of the paper casts postpartum depression as an adaptive response to threat (from whatever cause) to adequate mothering, and develops an argument for the evolutionary role of enacted social ties in the establishment of maternal responsiveness.     

Four chromosome replication origins in the archaeon Pyrobaculum calidifontis

Replication origins were mapped in hyperthermophilic crenarchaea, using high‐throughput sequencing‐based marker frequency analysis. We confirm previous origin mapping in Sulfolobus acidocaldarius, and demonstrate that the single chromosome of Pyrobaculum calidifontis contains four replication origins, the highest number detected in a prokaryotic organism. The relative positions of the origins in both organisms coincided with regions enriched in highly conserved (core) archaeal genes. We show that core gene distribution provides a useful tool for origin identification in archaea, and predict multiple replication origins in a range of species. One of the P. calidifontis origins was mapped in detail, and electrophoretic mobility shift assays demonstrated binding of the Cdc6/Orc1 replication initiator protein to a repeated sequence element, denoted Orb‐1, within the origin. The high‐throughput sequencing approach also allowed for an annotation update of both genomes, resulting in the restoration of open reading frames encoding proteins involved in, e.g., sugar, nitrate and energy metabolism, as well as in glycosylation and DNA repair.