Cellular and genetic mechanism of bacterial mercury resistance and their role in biogeochemistry and bioremediation

The emergence of carbapenemase-producing Enterobacteriaceae limits therapeutic options and presents a major public health problem. Resistances to carbapenems are mostly conveyed by metallo-beta-lactamases (MBL) including VIM, which are often encoded on resistance plasmids. We characterized four VIM-positive isolates that were obtained as part of a routine diagnostic screening from two laboratories in north-eastern Germany between June and August 2020. Whole-genome sequencing was performed to address (a) phylogenetic properties, (b) plasmid content, and (c) resistance gene carriage. In addition, we performed phenotypic antibiotic and mercury resistance analyses. The genomic analysis revealed three different bacterial species including C. freundii, E. coli and K. oxytoca with four different sequence types. All isolates were geno- and phenotypically multidrug-resistant (MDR) and the phenotypic profile was explained by the underlying resistance gene content. Three isolates of four carried nearly identical VIM-1-resistance plasmids, which in addition encoded a mercury resistance operon and showed some similarity to two publicly available plasmid sequences from sources other than the two laboratories above. Our results highlight the circulation of a nearly identical IncN-type VIM-1-resistance plasmid in different Enterobacteriaceae in north-eastern Germany.

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A Chromosomal Region Promoting Outcrossing in a Conifer

Genetics ◽

10.1093/genetics/159.3.1283 ◽

2001 ◽

Vol 159 (3) ◽

pp. 1283-1289

Author(s):

Claire G Williams ◽

Yi Zhou ◽

Sarah E Hall

Keyword(s):

Linkage Group ◽

Chromosomal Region ◽

Expressed Sequence Tag ◽

Balancing Selection ◽

Lethal Factor ◽

Genetic Mechanism ◽

Heterozygote Advantage ◽

Experimental Profile ◽

Gametic Selection ◽

Pinus Taeda L

Abstract Prefertilization mechanisms influencing selfing rates are thought to be absent in conifers. Outcrossing in conifers is promoted via an embryo-lethal system, but the genetic mechanism is poorly understood. This study is the first experimental profile of the genetic mechanism promoting outcrossing in conifers. Molecular dissection of a Pinus taeda L. selfed pedigree detected a chromosomal region identified as PtTX3020-RPtest9. Within this region, a semilethal factor was tightly linked (r = 0.0076) to a polymorphic expressed sequence tag (EST). The linkage group flanking the lethal factor showed strong heterozygote advantage. Using genotypic frequencies for the linkage group, three hypotheses about the semilethal factor could be tested: (1) the presence of a balanced lethal system, i.e., a lethal factor present in each of the two marker intervals; (2) gametic selection operative prior to fertilization; and (3) a stage-specific lethal factor. Selection acted via the embryo-lethal system. No support for a genetic mechanism operating prior to fertilization was found. The semilethal factor exerted no effect after embryo maturity. The genetic mechanism promoting outcrossing in P. taeda L. appears to have a balancing selection system due to either pseudo-overdominance or true overdominance.

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Human Handedness and Scalp Hair-Whorl Direction Develop From a Common Genetic Mechanism

Genetics ◽

10.1093/genetics/165.1.269 ◽

2003 ◽

Vol 165 (1) ◽

pp. 269-276

Author(s):

Amar J S Klar

Keyword(s):

Scalp Hair ◽

Single Gene ◽

Monozygotic Twins ◽

Hand Preference ◽

Genetic Mechanism ◽

Internal Organs ◽

Genetic Pathways ◽

Left Hand ◽

Learned Behavior ◽

Random Mixture

Abstract Theories concerning the cause of right- or left-hand preference in humans vary from purely learned behavior, to solely genetics, to a combination of the two mechanisms. The cause of handedness and its relation to the biologically specified scalp hair-whorl rotation is determined here. The general public, consisting of mostly right-handers (RH), shows counterclockwise whorl rotation infrequently in 8.4% of individuals. Interestingly, non-right-handers (NRH, i.e., left-handers and ambidextrous) display a random mixture of clockwise and counterclockwise swirling patterns. Confirming this finding, in another independent sample of individuals chosen because of their counterclockwise rotation, one-half of them are NRH. These findings of coupling in RH and uncoupling in NRH unequivocally establish that these traits develop from a common genetic mechanism. Another result concerning handedness of the progeny of discordant monozygotic twins suggests that lefties are one gene apart from righties. Together, these results suggest (1) that a single gene controls handedness, whorl orientation, and twin concordance and discordance and (2) that neuronal and visceral (internal organs) forms of bilateral asymmetry are coded by separate sets of genetic pathways. The sociological impact of the study is discussed.

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