Transient inflammatory-like state and microbial dysbiosis are pivotal in establishment of mucosal homeostasis during colonisation of germ-free mice.

The gut microbiota is increasingly recognised as a key-player in defining the health status of the gastrointestinal tract. Recently, we demonstrated that colonisation of healthy germfree mice with a conventional microbiota (conventionalisation) elicits temporal and region specific host-microbe communication responses that lead to the establishment of a microbiota-accommodating homeostatic state within 30 days. Here, the microbiota composition profiles, mucosal transcriptomes and plasma-analytes in germ-free and conventionalised C57/BL 6 J mice were assessed to decipher the features of the distinctive and pivotal events occurring four days after initiation of the conventionalisation process. The dominance of the microbial genera Helicobacter, Sphingomonas and Mucispirillum in the gut microbiota coincided with the transient mounting of proinflammatory responses in the mucosa and the transiently elevated levels of specific (inflammatory) cytokines and amines in plasma. The overrepresented microbes have previously been associated with the potential to cause disease under certain conditions, illustrating that conventionalisation proceeds through a transient state that resembles situations associated with dysbiosis. However, no overt mucosal inflammation was observed, suggesting a pivotal role of the overrepresented bacterial groups in priming and maturation of the immune system during the process of conventionalisation. These findings imply that the transiently elevated relative overgrowth of particular microbial genera functions as pivotal adjuvants to elicit the corresponding proinflammatory cascades, which precede the full maturation of the different arms of the immune system following these events and is required to achieve a microbiota-accommodating homeostasis in healthy animals.

Bacillus subtilis YxkJ is a secondary transporter of the 2-hydroxycarboxylate transporter family that transports L-malate and citrate.

The genome of Bacillus subtilis contains two genes that code for membrane proteins that belong to the 2-hydroxycarboxylate transporter family. Here we report the functional characterization of one of the two, yxkJ, which codes for a transporter protein named CimHbs. The gene was cloned and expressed in Escherichia coli and complemented the citrate-negative phenotype of wild-type E. coli and the malate-negative phenotype of the E. coli strain JRG4008, which is defective in malate uptake. Subsequent uptake studies in whole cells expressing CimHbs clearly demonstrated the citrate and malate transport activity of the protein. Immunoblot analysis showed that CimHbs is a 48-kDa protein that is well expressed in E. coli. Studies with right-side-out membrane vesicles demonstrated that CimHbs is an electroneutral proton-solute symporter. No indications were found for the involvement of Na(+) ions in the transport process. Inhibition of the uptake catalyzed by CimHbs by divalent metal ions, together with the lack of effect on transport by the chelator EDTA, showed that CimHbs translocates the free citrate and malate anions. Among a large set of substrates tested, only malate, citramalate, and citrate competitively inhibited citrate transport catalyzed by CimHbs. The transporter is strictly stereoselective, recognizing only the S enantiomers of malate and citramalate. Remarkably, though citramalate binds to the transporter, it is not translocated.

Effect of anterior hypothalamic and mammillary area lesions on territorial aggressive behaviour in male rats.

Adult male Wezob-rats were bilaterally lesioned in either the medial anterior hypothalamic area or the mammillary bodies. The behaviour of these animals when confronted with a male intruder within their own territory, was observed and recorded before and after lesioning and compared with the behaviour of sham-operated animals. Anterior hypothalamic lesions, including large parts of the anterior hypothalamus, the rostral part of the ventromedial hypothalamic nucleus and smaller caudal parts of the preoptic area, led to strong increases in defensive behaviour. This included a decreased tendency to investigate the intruder and an exaggerated defensive reaction when approached by the intruder. Ingestive behaviour and bodyweight were enhanced. Mammillary body lesions, including large parts of the ventral and dorsal premammillary nucleus, the caudal part of the arcuate nucleus, the medial mammillary nucleus, the posterior mammillary nucleus, the supramammillary peduncle and closely surrounding areas, led to a marked increase in offensive behaviour. This was characterized by high levels of initiatives and aggression towards an intruder. It is suggested that two distinct neural substrates exist in the medial hypothalamus, which normally modulate defensive (anterior medial hypothalamus) or offensive (posterior medial hypothalamus) aspects of intermale aggression.