Behavioral and genetic architecture of fear conditioning and related phenotypes.

Contextual fear conditioning is a form of Pavlovian learning during which an organism learns to fear previously neutral stimuli following their close temporal presentation with an aversive stimulus. In mouse models, freezing behavior is typically used to quantify learned fear. This dependent variable is the sum of multiple processes, including associative/configural learning, fear and anxiety, and general activity. To explore phenotypic constructs underlying contextual fear conditioning and correlated behaviors, as well as factors that may contribute to individual differences in learning and mental health, we tested BXD recombinant inbred strains previously found to show extreme contextual fear conditioning phenotypes and BXD parental strains, C57BL/6J and DBA/2J, in a series of tests including locomotor, anxiety, contextual/cued fear conditioning and non-associative hippocampus-dependent learning behaviors. Hippocampal expression of two previously identified candidate genes for contextual fear conditioning was also quantified. Behavioral and gene expression data were analyzed using exploratory factor analysis (EFA), which suggested five unique constructs representing activity/anxiety/exploration, associative fear learning, anxiety, post-shock freezing, and open field activity phenotypes. Associative fear learning and expression of one candidate gene, Hacd4, clusteredas a construct withinthefactor analysis. Post-shock freezingduring fear conditioning and expression of candidate gene Ptprd emerged as another unique construct, highlighting theindependenceof freezing after footshock from other fear conditioning variables in the current dataset.EFA results additionally suggest shared phenotypic variance in adaptive murine behaviors related to anxiety, general activity, and exploration. These findings inform understanding of fear learning and underlying biological mechanisms that may interact to produce individual differences in fear- and learning-related behaviors in mice.

Degradation of natural and synthetic polyesters under anaerobic conditions.

Often, degradability under anaerobic conditions is desirable for plastics claimed to be biodegradable, e.g. in anaerobic biowaste treatment plants, landfills and in natural anaerobic sediments. The biodegradation of the natural polyesters poly(beta-hydroxybutyrate) (PHB), poly(beta-hydroxybutyrate-co-11.6%-beta-hydroxyvalerate) (PHBV) and the synthetic polyester poly(epsilon-caprolactone) (PCL) was studied in two anaerobic sludges and individual polyester degrading anaerobic strains were isolated, characterized and used for degradation experiments under controlled laboratory conditions. Incubation of PHB and PHBV films in two anaerobic sludges exhibited significant degradation in a time scale of 6-10 weeks monitored by weight loss and biogas formation. In contrast to aerobic conditions, PHB was degraded anaerobically more rapidly than the copolyester PHBV, when tested with either mixed cultures or a single strained isolate. PCL tends to degrade slower than the natural polyesters PHB and PHBV. Four PHB and PCL degrading isolates were taxonomically identified and are obviously new species belonging to the genus Clostridium group I. The depolymerizing enzyme systems of PHB and PCL degrading isolates are supposed to be different. Using one isolated strain in an optimized laboratory degradation test with PHB powder, the degradation time was drastically reduced compared to the degradation in sludges (2 days vs. 6-10 weeks).

Metal tolerance and antibiotic resistance patterns of a bacterial population isolated from sea water.

The total aerobic heterotrophic and metal-resistant bacterial communities were studied in marine water. The resistance patterns, expressed as MICs, for 81 bacterial isolates to eight heavy metals were surveyed by using the agar dilution method. A great proportion of the isolates were sensitive to cadmium (99%), mercury (91%), zinc (84%) and cobalt (83%). On the other hand, 94%, 40%, 35% and 22% were resistant to lead, nickel, arsenate and copper, respectively. The majority of the tested strains (95.06%) were multiple metal-resistant, with pentametal resistance as the major pattern (25.9%). The response of the isolates to 11 tested antibiotics was tested and ranged from complete resistance to total sensitivity and multiple antibiotic resistance was exhibited by 70.38% of the total isolated population. The highest incidence of metal-antibiotic double resistance existed between lead and all antibiotics (100%), copper and penicillin (95%) and nickel and ampicillin (83.3%).