Many members of the sphingomonad genus isolated from different geological areas can degrade a wide variety of polycyclic aromatic hydrocarbons (PAHs) and related compounds. These sphingomonads such as Sphingobium yanoikuyae strain B1, Novosphingobium aromaticivorans strain F199, and Sphingobium sp. strain P2 have been found to possess a unique group of genes for aromatic degradation, which are distantly related with those in pseudomonads and other genera reported so far both in sequence homology and gene organization. Genes for aromatics degradation in these sphingomonads are complexly arranged; the genes necessary for one degradation pathway are scattered through several clusters. These aromatic catabolic gene clusters seem to be conserved among many other sphingomonads such as Sphingobium yanoikuyae strain Q1, Sphingomonas paucimobilis strain TNE12, S. paucimobilis strain EPA505, Sphingobium agrestis strain HV3, and Sphingomonas chungbukensis strain DJ77. Furthermore, some genes for naphthalenesulfonate degradation found in Sphingomonas xenophaga strain BN6 also share a high sequence homology with their homologues found in these sphingomonads. On the other hand, protocatechuic catabolic gene clusters found in fluorene-degrading Sphingomonas sp. strain LB126 appear to be more closely related with those previously found in lignin-degrading S. paucimobilis SYK-6 than the genes in this group of sphingomonads. This review summarizes the information on the distribution of these strains and relationships among their aromatic catabolic genes.
Effects of seed culture medium on the subsequent culture of L. helveticus growing on whey supplemented with yeast extract and peptones have been examined. Cells were inoculated when the maximum cellular activity was achieved, i.e. the maximum for the target function, the product of the specific growth rate with the undissociated lactic acid concentration. This function decreased when the nitrogen supplementation of the preculture medium was lowered, resulting only in an increase of the lag phase length of the culture, corresponding to a cellular adaptation to the new medium. On the contrary, when cells were not in the same physiological state, growth and production parameters were affected, maximum rates, as well as maximum biomass concentration. This occurred in case of the comparison of inocula carried out under pH control or not, or when various preculture lengths were tested.
Two probiotic strains, Lactobacillus agilis JCM 1048 and L. salivarius subsp. salicinius JCM 1230 isolated from chicken intestine, exhibited probiotic characteristics that can be applied for chicken production. After 7 days of probiotic feeding (FD7), the count of intestinal lactobacilli in the probiotic group (group P, n=10) was significantly (p<0.05) higher than that in the control group (group C, n=9). After 40 days of probiotic feeding (FD40), the lactobacilli and enterococci counts were stable but the Enterobacteriaceae number was significantly reduced (p<0.05). A total of 163 isolated lactobacilli were identified as the L. acidophilus/gallinarum group (49.7%), L. agilis (30.7%), L. salivarius (9.2%), L. reuteri (9.2%), and Lactobacillus spp. (1.2%). The probiotic lactobacilli positively affected the Lactobacillus biota in chickens at FD7, with a significant increase in the number (p<0.05) of L. agilis and group P. The viable counts of each Lactobacillus species at FD40, however, showed no differences between two groups. An increasing incidence of L. agilis was also noted with probiotic feeding. The probiotic effect of two strains resulted in significantly increased weight gains (10.7%) of group P in comparison with group C at FD40 (p<0.01).
The study provides the first evidence of the presence and abundance of bacterial population that coupled ferric iron reduction to aromatic compounds degradation in tropical irrigated paddy soils in the Philippines. Culturable phenol/benzoate degrading iron-reducing bacteria was enumerated by the most probable number (MPN) counts using phenol or benzoate as sole carbon source, and ferric oxide [Fe(OH)3] as the sole electron acceptor. Population density of phenol degrading iron-reducing bacteria (P-IRB) in irrigated paddy soil ranged from ≤102 to 108 g-1 dry soil, and increased with the progressive rice growth in rice cropping seasons; the study also revealed a significant rhizosphere effect on population of P-IRB. However, high enumeration of benzoate degrading iron-reducing bacteria (B-IRB) was obtained in all the tested soil samples averaging at 1.2×106 g-1 dry soil, and did not fluctuate significantly over the rice cropping seasons. Statistical data showed that less cropping density with aerated fallow and high nitrogen rate favored the population growth of P-IRB. However, results showed that population size of B-IRB was relatively insensitive to the effect of either seasonal or extrinsic factors tested in this study.
The effect of sodium acetate on the production of stereoisomers of lactic acid produced by Lactobacillus sakei NRIC 1071T and other lactic acid bacteria was studied. L. sakei NRIC 1071T started producing L-lactic acid at the early logarithmic phase and D-lactic acid at the late logarithmic phase. The activity of L-lactate dehydrogenase [EC 22.214.171.124, L-LDH] from the resting cells of L. sakei NRIC 1071T appeared at the early stage of the logarithmic phase during the growth, and the activity of D-lactate dehydrogenase [EC 126.96.36.199, D-LDH] at the late stage of the logarithmic phase. The resting cells and cell-free extracts of L. sakei NRIC 1071T did not produce DL-lactic acid from L- or D-lactic acid. Stained bands of L-LDH and D-LDH appeared in the cell-free extracts from the cells of L. sakei NRIC 1071T. Consequently, L. sakei conclusively produced L- and D-lactic acid by the action of L-LDH and D-LDH. This finding leads to the conclusion that lactate racemase [EC 188.8.131.52] does not exist in this strain. When the specific activity of LDHs (the total activity of L-LDH plus D-LDH) from the cells cultivated in the presence of sodium acetate is compared with that cultivated in its absence, the ratio of the activity between the cells cultivated in the former condition and those in the latter fell from 1.7 on the cell-free extracts to 1.3 on the preparation of the QAE-Toyopearl 550c chromatography. This result indicates that the amount of LDHs in the cells of L. sake NRIC 1071T cultivated in the presence of 50 mM sodium acetate was much more than that in the cells cultivated in the absence of sodium acetate. The shift of the type of stereoisomers of lactic acid from the DL-type to the L-type is discussed in the case of L. sakei strains.