Probiotic Bacteria May Become Dormant during Storage

The determination of bacterial viability in probiotic products is of economic, technological, and clinical significance. We compared four methods to enumerate three Bifidobacterium strains in fermented oat products during storage. A subpopulation of nonculturable cells retained a functional cell membrane typical of viable cells, indicating that probiotic bacteria become dormant during storage.     

Early succession of bacterial biofilms in paper machines

Formation of biofilms causes severe problems in paper machines, and hence financial costs. It would be preferable to prevent attachment of the primary-colonizing bacteria than to control the growth of secondary communities, which are sheltered by exopolysaccharide slime layers. We have therefore investigated the early succession of paper-machine biofilms by incubating stainless-steel test coupons in the process water-flow lines in two paper machines operating in slightly alkaline conditions in temperatures (45 and 49°C) supporting thermophilic microbes. Microbial succession was profiled using length heterogeneity analysis of PCR-amplified 16S rRNA genes (LH-PCR) and linking the sequence data of the created 16S rRNA gene libraries to the dominant LH-PCR peaks. Although the bacterial fingerprints obtained from the attached surface communities varied slightly in different samples, the biomarker signals of the dominating primary-colonizing bacterial groups remained high over time in each paper machine. Most of the 16S rRNA gene copies in the early biofilms were assigned to the genera Rhodobacter, Tepidimonas, and Cloacibacterium. The dominance of these sequence types decreased in the developing biofilms. Finally, as phylogenetically identical primary-colonizers were detected in the two different paper mills, the machines evidently had similar environmental conditions for bacterial growth and potentially a common source of contamination.     

Evolution of black grouse leks: female preferences benefit males in larger leks

Leks, communal display grounds in which males display and femalesonly attend to mate, represent one of the most remarkable outcomesof sexual selection. There have been no detailed studies thatcompare the behavior of males and females between leks of differentsizes to test if there is any benefit for male clumping andto test the many hypotheses suggested to explain lekking. Inthe black grouse, Tetrao tetrix, larger leks have many morefemale visits and copulations, leading to a higher average malemating success. Females visiting larger leks are also more likelyto mate, indicating that female preferences of males are importantfor the evolution of leks. Yearling males seldom copulate, buttheir presence on the lek increases the mating success of adultmales, suggesting that lek size per se and not only male qualityaffects female preferences for larger leks. The distributionof males over lek sizes agrees with a game theory model of idealfree distribution with unequal competitors, in which less competitivemales go to smaller leks.     

SEXUAL SELECTION IN A WOLF SPIDER: MALE DRUMMING ACTIVITY,BODY SIZE,AND VIABILITY

Females are often believed to actively choose highly ornamented males (males with extravagant morphological signals or intense sexual display), and ornaments should be honest signals of male viability. However, this belief is relying only on some pieces of empirical evidence from birds. Our study reports active female choice on sexual display that indicates male viability in spiders. We established trials in which we studied female choice in relation to male courtship drumming activity and body size. Females chose the most actively drumming males as mating partners, but the body size of the males did not seem to be selected. Male drumming activity turned out to be a good predictor of male viability, whereas male viability was independent of male body mass. Our results suggest that by actively choosing mates according to male drumming performance, but independently of male body mass, females are preferring viable males as mates. Because Hygrolycosa rubrofasciata males do not provide obvious direct benefits to their offspring, females may gain some indirect benefits; offspring may have higher chance of survival, or the offspring may inherit the attractiveness of their father.     

Responses of Male and Female Black Grouse to Male Vocal Display

The evolution of leks may be explained by several hypotheses. The ‘female preference’ hypothesis, which states that females favour males that have aggregated, has recently gained some empirical support. Low-quality, unattractive males may, however, settle near attractive males, as predicted by the ‘hotshot’ hypothesis. We tested whether black grouse Tetrao tetrix females use auditory cues to find the preferred leks, and whether males respond to vocal display emitted on leks. We conducted a playback experiment with male vocal display (rookooing) on leks, where the visiting females and displaying males were counted. The number of males tended to increase more on playback leks. Specifically, the number of 1-year-old males was greater on playback sites than on control sites. Also, the number of females, in relation to the lek size before the start of the experiment tended to increase. In addition, we used aviary playback trials to test whether females distinguish between single-male and multi-male displays. In a choice test, females showed greater preference for the ‘multi-male’ tape. The tendency for increased male numbers on playback leks resulted from increased visits of young, mobile males which were attracted to leks that they perceived to be large. This suggests a ‘hotshot’-type mechanism in the settlement of young males. Because females also responded to the supplemented auditory advertisement, or directly to the increased number of males, the ‘female preference’ hypothesis is also supported. Females may, at least in part, base their decision of which lek to visit on auditory cues, but visual contact to males may be also needed.     

Change of pupal size of Panolis flammea (Lepidoptera; Noctuidae) and Bupalus piniarius (Geometridae) in response to concentration of industrial pollutants in their food plant

Summary Larvae of Panolis flammea and Bupalus piniarius were reared in the laboratory on needles of Scots pine affected by industrial air pollutants in Finland. Needles were collected at different distances from a distinctive source of emission along two 9-km-long transects, and from independent control plots. The elemental composition of the needles used as larval food was analysed. Pupal weight, length and width were negatively correlated wiht the distance from the source of emission. The elemental composition of the pine needles explained 24–53% of the variation in pupal weight. Most of the explained variation was assoicated with the concentration of heavy meals in the pine needles.     

The ability of isolated myocardial cells of the rat to contract at temperatures near freezing point

1. 1.|Single spontaneously-beating myocardial cells were prepared by enzymatic isolation from rat heart ventricles. Using a TV camera and videotape recorder, beating parameters were characterized with respect to temperature.

2. 2.|The cells obtained showed two types of contractions: (a) action-potential-coupled, fast contractions, which could be triggered electrically but sometimes also occurred spontaneously; and (b) a phasic type of contraction which occurs spontaneously as a slowly (25–200 μm s⁻¹) proceedings wave through the cell and is not coupled to the action potential.

3. 3.|Both the spontaneous phasic and electrically-triggered fast contractions continued down to about 0°C, where the cells went into an irreversible contracture, but recovered if the temperature was raised before the contracture occurred.

4. 4.|In physically-contracting cells, the beat rate and the velocity of the contraction wave were temperature dependent showing a linear relationship on an Arrhenius plot; apparent activation energies were 31 and 54 kJ mol⁻¹, respectively.

5. 5.|When fast contractions were triggered by electric field stimulation, the threshold of cells was reduced as temperature rose. The rheobase values showed that cell excitability decreased more steeply when the temperature fell below 20°C. This change could not be seen in the values of chronaxie, which showed a linear relationship on the Arrhenius plot within the whole temperature range used (6–35°C).

6. 6.|It is concluded that the lower temperature limit is not the same for all structural levels of the rat heart. Myocardial cells are able to contract still at the freezing point while mechanisms initiating the heart beat require higher temperatures to be functional.

Bark beetle diversity at different spatial scales

To determine how the scale of observation affects ecological patterns we studied bark beetle (Coleoptera, Scolytidae) diversity in southern Finland. A block covering 160 × 160 m of a forest was delimited in four stands of different site types. Each block was divided into 256 squares (10 × 10 m) in which the occurrence of bark beetle species was recorded. In addition, environmental variables describing site type, trees, and breeding material appropriate for bark beetles were measured. The species presence/absence data were combined at different scales of resolution (10 × 10 m. 20 × 20 m, 40 × 40 m, 80 × 80 m, 160 × 160 m). At the finest scale a recently thinned pine stand showed relatively high diversity compared to other study stands due to a few evenly distributed and abundant species. However, the species diversity increased faster toward larger scales in mature spruce stands with several sporadically distributed species. According to logistic regression analyses, breeding material and site characteristics explained the occurrence of most beetle species. However, these variables did not explain the occurrence of the six most frequent species, probably because the factors regulating their distribution and occurrence operate at larger scales.