Microbial Amino Acid Composition Research Articles

Acidic proteomes are linked to microbial alkaline preference in African lakes

Microbial amino acid composition (AA) reflects adaptive strategies of cellular and molecular regulations such as a high proportion of acidic AAs, including glutamic and aspartic acids in alkaliphiles. It remains understudied how microbial AA content is linked to their pH adaptation especially in natural environments. Here we examined prokaryotic communities and their AA composition of genes with metagenomics for 39 water and sediments of East African lakes along a gradient of pH spanning from 7.2 to 10.1. We found that Shannon diversity declined with the increasing pH and that species abundance were either positively or negatively associated with pH, indicating their distinct habitat preference in lakes. Microbial communities showed higher acidic proteomes in alkaline than neutral lakes. Species acidic proteomes were also positively correlated with their pH preference, which was consistent across major bacterial lineages. These results suggest selective pressure associated with high pH likely shape microbial amino acid composition both at the species and community levels. Comparative genome analyses further revealed that alkaliphilic microbes contained more functional genes with higher acidic AAs when compared to those in neutral conditions. These traits included genes encoding diverse classes of cation transmembrane transporters, antiporters, and compatible solute transporters, which are involved in cytoplasmic pH homeostasis and osmotic stress defense under high pH conditions. Our results provide the field evidence for the strong relationship between prokaryotic AA composition and their habitat preference and highlight amino acid optimization as strategies for environmental adaptation.

Effects of Dietary Crude Protein Levels on Fecal Crude Protein, Amino Acids Flow Amount, Fecal and Ileal Microbial Amino Acids Composition and Amino Acid Digestibility in Growing Pigs.

Simple SummaryThe purpose of this experiment was to evaluate a low protein corn-soybean meal-based diet with the same Lys, Met + Cys, Thr and Trp level as a high protein diet on fecal crude protein (CP), amino acid (AA) flow amount, AA digestibility and fecal and ileal microbial AA composition in growing pigs. Eighteen pigs with an initial body weight of (30 ± 1.35) kg were randomly divided into three groups, with six replicates in each group, and fed a corn-soybean meal-based diets with 12%, 15% and 18% CP levels, respectively. Our aim was to explain whether the addition of four crystalline essential AAs (EAA) to a low diet affected the digestibility of protein-bound NEAA (non-essential amino acid) and EAA and the composition of microbial AA in ileum and feces.The purpose of this experiment was to evaluate the effects of low protein corn-soybean meal-based diets on fecal CP, amino acid (AA) flow amount, AA digestibility and fecal and ileal microbial AA composition in growing pigs. Eighteen pigs (initial body weight = 30 ± 1.35) were randomly divided into three groups and fed with basal diets with CP levels of 12%, 15% and 18%, respectively. The Lys, Met + Cys, Thr and Trp level in the 12% CP and 15% CP groups is the same as 18% CP group by the addition of four crystalline Lys, Met + Cys, Thr and Trp to the diet. The results showed that with the decrease of dietary CP level from 18% to 12%, the fecal total nitrogen (N), CP and total AA (TAA) flow amount decreased linearly (p < 0.05). Dry matter (DM) digestibility, CP digestibility, TAA digestibility, essential amino acid (EAA) digestibility and non-essential amino acid (NEAA) digestibility increased linearly with the decrease of dietary CP concentration from 18% to 12%. Compared with 18% CP group, the flow amount of Asp, Ser, Glu, Gly, Tyr, Val, Leu and Phe in feces of pigs in the 15% CP group and 12% CP group decreased significantly, while the flow amount of Arg in the 15% CP group was lower than that in the 18% CP group and 12% CP group. The fecal microbial N and AA of the 15% CP group were higher than those of the 18% CP and 12% CP groups. Fecal TAA flow amount decreased linearly with the decrease of the dietary CP levels from 18% to 12%. Fecal TAA and NEAA flow amount also decreased linearly with the decrease of dietary CP level from 18% to 12%. Except for Glu, Gly, Met, Tyr, Thr and Phe, there were significant differences among the three groups in the composition of 17 kinds of AAs in fecal microorganisms. Among the 17 AA compositions of ileal microorganisms, except Tyr and Lys, the other AAs were significantly different among the three groups (p < 0.05)

The effects of different dietary crude protein level on faecal crude protein and amino acid flow and digestibility in growing pigs

ABSTRACTThis study was conducted to evaluate the effects of dietary crude protein (CP) level on faecal CP and amino acid (AA) flow and digestibility, faecal and ileal digesta microbial AA composition. Eighteen Duroc × Landrace × Yorkshire barrows (60 ± 1.43 kg) were randomly divided into 3 groups with 6 barrows in each, and fed a maize–soybean meal diet at the 10% (L-CP), 13% (M-CP) and 16% (H-CP) CP levels. The results indicated the faecal total N, CP, total AA (TAA) flow increased linearly (P < 0.05) whereas dietary CP concentration increased from 10% to 16%. The DM digestibility, CP digestibility, TAA digestibility, essential amino acid and non-essential amino acid digestibility decreased linearly (P < 0.05), whereas dietary CP concentration increased from 10% to 16%. Compared with pigs in M-CP and L-CP groups, pigs in the H-CP group had higher Asp, Cys, His, Arg flow in the faeces (P < 0.05). Compared with pigs in the L-CP group, pigs in M-CP and H-CP groups had less faecal Glu, Ala, Tyr, Pro, Val, Ile, Leu and flow (P < 0.05). Faecal microbial N and AA in the L-CP group was the highest in three groups. Pigs fed a corn–soybean meal-based diet reduced in protein concentration have lower faecal N flow.

Effects of rice straw particle size on digesta particle size distribution, nitrogen metabolism, blood biochemical parameters, microbial amino acid composition and intestinal amino acid digestibility in goats

Effects of rice straw particle size and physically effective neutral detergent fiber (peNDF) on particle size distribution of different digestive tract, nitrogen (N) metabolism, blood biochemical parameters, microbial amino acid (AA) composition and intestinal AA digestibility in goats were investigated. A 4 × 4 Latin square design was employed using four mature Liuyang black goats fitted with permanent ruminal, duodenal, and terminal ileal fistulae. During each of the four periods, goats were offered one of four diets that were similar in chemical composition, but varied in particle sizes and peNDF through alteration of the theoretical cut length of rice straw (10, 20, 40 and 80 mm, respectively). Dietary peNDF contents of four diets were 17.4, 20.9, 22.5 and 25.4%, respectively. Results showed that increasing particle size of rice straw and dietary peNDF significantly affected the particle size distributions of digesta in rumen, duodenum and ileum, except feces. However, increasing particle size of rice straw and peNDF did not affected N metabolism in goats, except the increased apparent N digestibility in rumen and large intestine, and the decreased apparent N digestibility in small intestine. Furthermore, increasing particle size of rice straw and peNDF showed little influence on the profile of blood biochemical parameters, microbial AA composition and intestinal AA digestibility in goats.

Application of the Cornell Net Carbohydrate and Protein model for cattle consuming forages.

Accurate prediction of forage biological values and performance with animals fed forages requires accurately accounting for factors that influence animal requirements and feedstuff utilization. The Cornell Net Carbohydrate and Protein System (CNCPS) is an application model that uses a combination of mechanistic and empirical approaches to account for the effects of variation in animal factors and feed carbohydrate and protein fractions on animal performance. Thus, accurate animal and environmental descriptions, DMI, feed carbohydrate, and protein fractions and their digestion rates are required inputs. In 25 growth periods with calves fed high-forage diets, the CNCPS accounted for 74, 81, and 83%, respectively, of the variation in ADG predicted to be supported by the ME, metabolizable protein, and essential amino acid intake, the first-limiting of all three accounting for 81% of the variation with a -1% bias. Thus, the CNCPS can be used to accurately describe forage quality and the effects of changes in forage composition on animal performance. The model was sensitive to variations in NDF, CP, protein solubility, NDF and starch digestion rates, feed and microbial amino acid composition, maintenance protein requirement, body protein amino acid content, and the coefficient of efficiency of use of absorbed protein. Analysis of several trials indicates an improved efficiency of ME use with improved amino acid balances. Uses of the CNCPS discussed include interpreting, planning and applying research, teaching, developing tables of requirements and biological values for feeds, complex nutritional accounting, and predicting performance and profits.

Effects of rape-seed oil supplementation on digestion, microbial protein synthesis and duodenal microbial amino acid composition in ruminants

The effects of rape-seed oil supplementation on digestion and efficiency of microbial protein synthesis were estimated in four Friesian bulls fitted with rumen and simple-T duodenal fistula in 2 × 2 change-over design. The basal diet was 4.8 kg day −1 dry matter (DM) fresh cut grass silage and 2.6 kg day −1 DM rolled barley. The test feed (RSO) was formulated by supplementing the basal diet with 0.5 kg rape-seed oil. The bulls were fed at 07:00 and 19:00 h daily. Digestion in the rumen was measured by spot sampling of duodenal digesta, using the double marker method. Amino acid (AA) composition was determined from the microbial mass separated from duodenal digesta. A daily supplement of RSO showed no significant effect on rumen pH. Rumen total volatile fatty acids concentration decreased ( P = 0.09). Molar proportion of acetate and butyrate decreased ( P = 0.01) while propionate proportion increased ( P = 0.002). Rumen protozoal population decreased from 4.2 × 10 5 to 2.9 × 10 51 −1. Whole tract and ruminal digestion of organic matter was lower for RSO compared with basal diet. The mean N intake was 160 g day −1 for basal and 153 g day −1 for RSO and the corresponding duodenal flow was 140 g day −1 and 146 g day −1 with microbial N flow of 78 g day −1 and 86 g day −1, respectively. Duodenal microbial AA N (g per 100 g microbial N) was 85.0 for basal and 64.6 for RSO with decreased ( P = 0.02) lysine and methionine content of microbial AA. The rate of passage ( K p) was reduced with extended fibre retention time.