Remnant gastritis in gastric cancer patients causes loss of muscle mass 6 months after gastrectomy: a retrospective cohort study of Helicobacter pylori infection.

PURPOSE: In this study, we assessed the relationship between remnant gastritis and muscle mass loss and then investigated the potential relationship between Helicobacter pylori (HP) infection and remnant gastritis and muscle loss. METHODS: We reviewed the medical records of 463 patients who underwent distal gastrectomy between January 2017 and March 2020. Of these patients, 100 with pStage I after laparoscopic surgery were included in this analysis. RESULTS: A multivariate analysis showed that the total Residue, Gastritis, Bile (RGB) classification score, which indicates the degree of gastritis, was significantly associated with the rate of change (rate of decrease) in the psoas muscle area (PMA) during the first 6 months after surgery (p = 0.014). Propensity score matching was performed according to HP infection, and the rate of change in the PMA and the degree of remnant gastritis in 56 patients were compared. Neither was significantly associated with HP infection. CONCLUSIONS: Remnant gastritis did contribute to psoas muscle mass loss during the initial 6 months after gastrectomy, and HP infection was not significantly associated with either remnant gastritis or psoas muscle mass loss. Nevertheless, the potential for HP eradication to prevent muscle loss and improve the survival prognosis for gastrectomy patients merits further research.

Efficacy and safety of patient-controlled thoracic epidural analgesia alone versus patient-controlled intravenous analgesia with acetaminophen after laparoscopic distal gastrectomy for gastric cancer: a propensity score-matched analysis.

BACKGROUND: Laparoscopic gastrectomy is a common procedure for early gastric cancer treatment. Improving postoperative pain control enhances patient recovery after surgery. The use of multimodal analgesia can potentially enhance the analgesic effect, minimize side effects, and change the postoperative management. The purpose of this study was to evaluate and compare the efficacies of the use of patient-controlled intravenous analgesia with regular acetaminophen (PCIA + Ace) and patient-controlled thoracic epidural analgesia (PCEA) for postoperative pain control. METHODS: We retrospectively collected the data of 226 patients who underwent laparoscopic distal gastrectomy (LDG) with delta-shaped anastomosis between 2016 and 2019. After 1:1 propensity-score matching, we compared 83 patients who used PCEA alone (PCEA group) with 83 patients who used PCIA + Ace (PCIA + Ace group). Postoperative pain was assessed using a numeric rating scale (NRS) with scores ranging from 0 to 10. An NRS score ≥ 4 was considered the threshold for additional intravenous rescue medication administration. RESULTS: Although NRS scores at rest were comparable between the PCEA and PCIA + Ace groups, NRS scores of patients in the PCIA + Ace group during coughing or movement were significantly better than those of patients in the PCEA group on postoperative days 2 and 3. The frequency of additional rescue analgesic use was significantly lower in the PCIA + Ace group than in the PCEA group (1.1 vs. 2.7, respectively, p < 0.001). The rate of reduction or interruption of the patient-controlled analgesic dose was higher in the PCEA group than in the PCIA + Ace group (74.6% vs. 95.1%, respectively, p = 0.0002), mainly due to hypotension occurrence in the PCEA group. Physical recovery time, postoperative complication occurrence, and liver enzyme elevation incidence were not significantly different between groups. CONCLUSIONS: PCIA + Ace can be safely applied without an increase in complications or deterioration in gastrointestinal function; moreover, PCIA + Ace use may provide better pain control than PCEA use in patients following LDG.

Relative dose intensity and 1-year psoas muscle index reduction rate as prognostic factors in gastric cancer patients with postoperative adjuvant chemotherapy.

BACKGROUND: Higher relative dose intensity (RDI) of chemotherapy improves the clinical outcomes of various cancers. The psoas muscle index (PMI) is related to sarcopenia, and patients with low PMI have worse prognoses. However, few studies have demonstrated its clinical relevance in gastric cancer. METHODS: This retrospective study included 188 stage II/III gastric cancer patients who had undergone curative gastrectomy between January 2013 and March 2017, 124 of whom had received postoperative S-1 adjuvant chemotherapy. RESULTS: Per receiver operating characteristic analysis, patients were divided into high and low RDI groups, between which relapse-free survival differed marginally significantly and disease-specific survival differed significantly. In patients who received adjuvant chemotherapy, multivariate analysis found that high RDI and low PMI reduction rate 1 year after surgery were significantly associated with better relapse-free survival. Low RDI can be predicted by a combination of low preoperative PMI and non-distal gastrectomy, whereas high PMI reduction rate at 1 year can be affected by non-distal gastrectomy. CONCLUSION: High RDI with preserved psoas muscle up to 1 year after gastrectomy may be associated with prognoses in gastric cancer requiring postoperative adjuvant chemotherapy. Since RDI and PMI reduction rate can be predicted preoperatively, respectively, interventional consideration is possible for optimal adjuvant therapy in gastric cancer.

Inhibitory effect of aspirin on inflammation-induced lung metastasis of cancer cells associated with neutrophil infiltration.

PURPOSE: Systematic inflammation has been reported to contribute to cancer progression through various mechanisms; however, the exact mechanism is still the subject of research. In this study, we evaluated the influence of systematic inflammation on lung metastasis, using a murine abdominal sepsis model, and assessed its relationship with pneumonia after curative esophagectomy in patients with esophageal cancer. METHODS: We used a murine abdominal sepsis model given highly metastatic osteosarcoma, to reveal the mechanism of systematic inflammation and its potential for lung metastasis. The therapeutic effect of aspirin (ASA) in preventing distant metastasis was also investigated. Subsequently, we analyzed, retrospectively, the relationship between pneumonia and lung metastasis after esophagectomy in patients who underwent esophagectomy at Keio University between January, 2007 and October, 2020. RESULTS: Abdominal sepsis provoked lung injury in the acute phase. ASA inhibited the recruitment of neutrophils triggered by the lung injury, and it also suppressed lung metastasis. Our retrospective study revealed that lung metastasis was more frequent in patients with postoperative pneumonia. CONCLUSIONS: Postoperative acute lung injury is associated with a higher risk of lung metastasis. ASA may be a potential preoperative treatment for inhibiting lung metastasis by preventing the recruitment of neutrophils.

Clinical predictors of early postoperative recurrence after radical esophagectomy for thoracic esophageal cancer.

PURPOSE: Esophagectomy for esophageal cancer has a high incidence rate of early postoperative recurrence and death. This study aimed to identify the clinical and pathological features in early recurrence cases and to confirm the usefulness of prediction using these factors for effective adjuvant therapy and postoperative surveillance. METHODS: One hundred and twenty five patients who developed postoperative recurrence after undergoing radical esophagectomy for thoracic esophageal cancer were classified into two groups as follows: those with early recurrence at ≤ 6 months and those with nonearly recurrence at > 6 months after surgery. After identifying related factors of early recurrence, usefulness of these factors for prediction were examined in all patients with and without recurrence. RESULTS: The analysis cohort consisted of 43 and 82 patients in the early and nonearly recurrence groups, respectively. In multivariate analysis, factors associated with early recurrence were higher initial levels of tumor markers (squamous cell carcinoma [SCC] ≥ 1.5 ng/ml in tumors, except for adenocarcinoma, and carcinoembryonic antigen [CEA] ≥ 5.0 ng/ml in adenocarcinoma) and higher venous invasion (v), i.e., ≥ 2 (p = 0.040 and p = 0.004, respectively). The usefulness of these two factors for recurrence prediction was confirmed in 378 patients, including 253 patients without recurrence. Patients with at least one of the two factors had significantly higher early recurrence rates than those without any factors in pStages II and III (odds ratio [OR], 6.333; p = 0016 and OR, 4.346; p = 0.008, respectively). CONCLUSIONS: Early recurrence of thoracic esophageal cancer (i.e., during ≤ 6 months after esophagectomy) was associated with higher initial tumor marker levels and pathological findings of v ≥ 2. The combination of these two factors is useful as a simple and critical predictor of early postoperative recurrence.

Elevation of the Prognostic Factor Plasma Fibrinogen Reflects the Immunosuppressive Tumor Microenvironment in Esophageal Squamous Cell Carcinoma.

INTRODUCTION: Despite previous reports on the clinical significance of plasma fibrinogen (FNG) levels as a prognostic indicator of ESCC, its underlying mechanism remains unclear. This study aimed to validate the prognostic impact of plasma FNG levels and clarify its relationship with primary tumors in patients with esophageal squamous cell carcinoma (ESCC). METHODS: The prognostic impact of FNG was evaluated in patients with ESCC who underwent esophagectomy between 2000 and 2019. The RNA sequencing of the primary ESCC site, which was from pre-operative biopsy, was performed, followed by immune profile characterization using an immunogram. Those profiles were assessed via the immunohistochemical staining of tumor-associated macrophages (TAMs) and clinical response to nivolumab. RESULTS: Multivariate analysis identified FNG as a significant prognostic factor in ESCC. The immunogram suggested an immunosuppressive tumor environment in the high-FNG group. Immunostaining with the TAM markers CD163 and CD204, revealed that the high-FNG group had significantly higher number of TAMs compared with the low-FNG group. The immunosuppressive characteristics were clinically validated in patients with metastatic ESCC; those who had elevated FNG levels showed poor response to nivolumab. CONCLUSION: This study successfully validated the prognostic impact of plasma FNG levels in an expanded cohort with ESCC. Accordingly, our findings showed that increased plasma FNG reflects an immunosuppressive tumor microenvironment that facilitates tumor progression and poor responses to nivolumab.

Clinical Features of Recurrence Pattern with Lung Metastasis After Radical Esophagectomy for Thoracic Esophageal Cancer.

BACKGROUND: One of the difficulties in the treatment of esophageal cancer surgery is the high rate of postoperative recurrence. After esophagectomy, distant metastatic recurrence frequently occurs in the lung. This study aimed to determine the clinical features of a recurrence pattern with lung metastasis. METHODS: The current study analyzed data from 138 patients who had postoperative recurrence of esophageal cancer after a radical esophagectomy. According to the recurrence pattern at the time of initial diagnosis, the patients were classified into two groups as follows: those with lung metastasis and those without. RESULTS: Twenty-three of the 138 investigated patients had a recurrence pattern with lung metastasis. Salvage surgery and postoperative pneumonia (p = 0.041 and 0.030, respectively) were identified as risk factors for recurrence pattern with lung metastasis in multivariate analysis. When we compared the sites of primary esophageal tumors, we found that the frequencies of distant metastases, such as lung and liver metastases, as well as pleural/peritoneal dissemination, were higher in the mid and distal esophageal tumors. Patients with a recurrence pattern showing lung metastasis alone had a better overall and post-recurrence survival than those with other recurrence patterns (p < 0.001 and p < 0.001). CONCLUSIONS: In patients who had postoperative recurrence after esophagectomy for thoracic esophageal cancer, salvage surgery, and postoperative pneumonia were significantly related to recurrence pattern with lung metastasis. Postoperative recurrence with lung metastasis alone had a better prognosis than other recurrence patterns; therefore, when pulmonary recurrence is suspected, performing intensive examinations for early diagnosis is critical.

Dismal prognosis of elderly gastric cancer patients who underwent gastrectomy with American Society of Anesthesiologists (ASA) 3.

BACKGROUND: Although the American Society of Anesthesiologists (ASA) score of 3 is relatively common in elderly patients, there have been few debates on the indications for gastrectomy in elderly gastric cancer (GC) patients with ASA3. Therefore, this study aimed to investigate gastrectomy's clinical relevance in elderly patients with GC and ASA3. METHODS: We retrospectively analyzed 228 consecutive elderly GC patients (aged ≥ 75 years) without prior treatments who underwent curative gastrectomy between 2013 and 2017. RESULTS: Thirty-three patients with ASA3 showed significantly poorer prognosis than those with ASA1 and 2 (p = 0.004). The multivariate Cox proportional hazards model showed that ASA3 (p = 0.021) and pStage (p = 0.007) were independent prognostic factors, respectively. Elderly GC patients with pStage III and ASA3 exhibited uniquely dismal prognosis (p < 0.001); however, several survivors were still confirmed. Postoperative complications (PCs) were only the final remnant independent prognostic factor (p = 0.020) among the 33 elderly GC patients with ASA3, where dead patients included cancer-specific and other deaths, especially pneumonia. PCs were independently associated with prognostic nutritional index (PNI) (< 42.7) in elderly GC patients, and the most frequent complication was pneumonia, which was significantly associated with ASA3 and marginally associated with PNI in a multivariate analysis. CONCLUSIONS: ASA3 has a dismal prognosis after curative gastrectomy in the elderly GC patients, but the number of survivors was confirmed. Curative gastrectomy is not considered contraindicated even in elderly GC with ASA3. Preoperative malnutrition is associated with PCs, which proposing preoperative nutritional intervention in the context of treatment strategy for the elderly GC patients with ASA3.

Exploratory prospective study of the influence of radical esophagectomy on perioperative physical activity in patients with thoracic esophageal cancer.

Sarcopenia, which involves two important aspects, namely skeletal muscle loss and decreased physical function, was suggested as a poor prognostic factor in esophageal cancer surgery. The purpose of this study was to clarify the perioperative change in daily physical activity and propose effective preventive strategies. We prospectively enrolled patients with esophageal cancer who were scheduled to undergo radical esophagectomy. Their daily physical activities were recorded using an accelerometer before surgery, immediately after discharge, and 6 months after surgery. The relationships of physical activity level and the perioperative factors, especially skeletal muscle change, with the risk factors of low daily activity level were investigated. The data of 20/28 enrolled patients were analyzed. The mean activity level of the 20 patients decreased after discharge and subsequently recovered on postoperative month 6. The percentage of activity levels >1.5 metabolic equivalents/day after discharge significantly correlated to the change rate in total muscle cross-sectional area from baseline to POM 6 (r = 0.452, P = 0.045). In a stepwise multiple regression analysis, age, neoadjuvant chemotherapy, and anastomotic leakage were identified as negative associated factors of activity time at >1.5 metabolic equivalents at postoperative month 6. Activity level immediately after discharge was significantly associated with skeletal muscle loss at postoperative month 6 in patients with esophageal cancer who underwent esophagectomy. Elderly patients and patients who received neoadjuvant chemotherapy and had an anastomotic leakage might require intensive prevention. Prospective interventions aimed at increasing daily activity can prevent sarcopenia.

Short- and long-term outcomes of laparoscopic distal gastrectomy versus open distal gastrectomy for gastric cancer in overweight patients.

PURPOSE AND BACKGROUND: Gastrectomy for gastric cancer in overweight patients is associated with a high incidence of postoperative complications and difficulties in achieving adequate lymph node dissection. We conducted this study to compare the outcomes of laparoscopic and open distal gastrectomy (ODG) for gastric cancer in overweight Japanese patients. METHODS: This retrospective study analyzed data from 180 patients with a body mass index ≥ 25 who underwent distal gastrectomy for pStage I-III gastric cancer. Postoperative complications, the number of harvested lymph nodes, and long-term survival were compared between ODG and laparoscopic distal gastrectomy (LDG). RESULTS: Postoperative complications of Clavien-Dindo (CD) grade ≥ 2 and ≥ 3 were significantly higher after ODG than after LDG (p < 0.001 and p = 0.004). Multivariate analysis identified age and ODG as factors related to complications of CD ≥ 2 (p = 0.014 and 0.002). The number of harvested lymph nodes at region 4sb was significantly higher in LDG for patients with pStage III disease. The 5-year lymph node recurrence-free survival tended to be better in LDG; however, no difference was found between ODG and LDG at any pathological stage. There were no significant differences in the 5-year overall and recurrence-free survival rates after ODG vs. LDG. CONCLUSIONS: LDG for gastric cancer appears to be associated with a lower incidence of postoperative complications than ODG, without compromising long-term survival, even for overweight patients.

Impact of loss of skeletal muscle mass within 6-12 months after gastrectomy and S1 adjuvant chemotherapy on the survival prognosis of elderly patients with gastric cancer.

BACKGROUND AND PURPOSE: We investigated the impact of postoperative changes in the psoas muscle mass index (PMI) after gastrectomy and S1 adjuvant chemotherapy (AC) on the long-term outcomes of elderly patients with gastric cancer. METHODS: We reviewed the medical records of 228 patients aged over 75 years, who underwent distal, proximal, or total gastrectomy between January, 2013 and March 2017. Among these patients, 78 with pStage IIA-IIIC who survived for at least 1 year without recurrence after gastrectomy were the subjects of this analysis. RESULTS: The log-rank test using the cut-off value from the rate of change in PMI from 6 to 12 months after gastrectomy (late rate of decrease) showed significantly poorer prognosis for the group above the cut-off value for both overall survival (OS) and recurrence-free survival (RFS) (RFS: PMI decrease ≥ 1.55%, p < 0.001; OS: PMI decrease ≥ 1.55%, p < 0.001). Patients with a relative dose intensity of S1 below 68.7% and a late rate of decrease in PMI above 1.55% were found to have a poor prognosis. CONCLUSION: It is necessary to prevent decline in the PMI of elderly patients from 6 months after gastrectomy and to administer adjuvant chemotherapy with about two-thirds or more RDI of S1 to improve their survival prognosis.

Relationship Between Early Postoperative Change in Total Psoas Muscle Area and Long-term Prognosis in Esophagectomy for Patients with Esophageal Cancer.

PURPOSE: Postoperative sarcopenia following esophagectomy for esophageal cancer has become a severe problem due to the increasing number of elderly patients undergoing surgery. This study aimed to clarify the relationship between early postoperative skeletal muscle change and cancer prognosis, and propose effective interventions to prevent sarcopenia. METHODS: This study retrospectively analyzed 152 patients who underwent esophagectomy for esophageal cancer. Total psoas muscle area (TPA) was measured before surgery as baseline and on postoperative day 7 (± 2). The effect of early postoperative skeletal muscle loss on 5-year survival was investigated. Moreover, 5-year survival in patients with postoperative complications and a high inflammatory status, which were previously reported as poor prognostic factors of esophageal cancer, was also investigated. RESULTS: Among the 152 patients, 52 (34.2%) showed a decrease in TPA, while 100 (65.8%) maintained their TPA. The TPA decreasing group exhibited poor 5-year overall survival (OS) (p = 0.003) and 5-year recurrence-free survival (RFS) (p < 0.001). The TPA decreasing group also showed a poor 5-year OS in patients who developed severe postoperative complications (p = 0.015). Multivariate analyses showed that decreased TPA was found to be independently associated with OS (p = 0.017) as well as RFS (p = 0.002). CONCLUSIONS: Our findings suggested a relationship between decreased TPA within 1 week after esophagectomy and long-term prognosis among patients with esophageal cancer. If TPA can be maintained, the prognosis was better even in cases with serious complications.

C-reactive protein adjusted for body mass index as a predictor of postoperative complications following laparoscopic gastrectomy for gastric cancer.

PURPOSE: This study aimed to clarify the relationship between obesity and postoperative C-reactive protein (CRP) and assess the usefulness of obesity status-adjusted CRP levels for predicting early complications following laparoscopic gastrectomy for gastric cancer. METHODS: This study retrospectively analyzed 527 patients who underwent laparoscopic gastrectomy for gastric cancer between January 2013 and March 2019. Patients were classified into three groups according to body mass index (BMI): BMI < 20; BMI ≥ 20 to < 25; and BMI ≥ 25. The correlation between BMI and perioperative CRP was investigated in 447 patients, excluding 80 with postoperative complications. The optimal CRP cutoff value of Clavien-Dindo (CD) grade ≥ 3 for predicting severe complications for each group was determined. RESULTS: BMI was significantly correlated with CRP on postoperative day (POD) 3 (p < 0.001) in 447 patients without complications. According to the receiver operating characteristic curve analysis, CRP cutoff values on POD 3 for predicting severe complications were 92.4, 111.1, and 171.9 in the BMI < 20, BMI ≥ 20 to < 25, and BMI ≥ 25 groups, respectively. In multivariate analysis for CD grade ≥ 3 complications, cardiac history and POD 3 CRP levels higher than the adjusted cutoff were identified as independent factors significantly associated with severe complications (p = 0.021 and 0.015, respectively). CONCLUSION: CRP cutoff values on POD 3 adjusted for BMI were useful for predicting severe complications in gastrectomy for gastric cancer.

Association of preoperative sarcopenia with postoperative dysphagia in patients with thoracic esophageal cancer.

BACKGROUND: The purpose of the current study was to clarify the relationship between clinical features of dysphagia after esophagectomy and preoperative sarcopenia. METHODS: A total of 187 cases were included in the current study. The psoas cross-sectional area on pre-treatment computed tomography was measured in thoracic esophageal cancer patients who underwent curative resection. The psoas muscle index (PMI) cut-off levels for sarcopenia were 6.36 cm2/m2 for men and 3.92 cm2/m2 for women. Swallowing function was evaluated using videofluoroscopic swallowing study (VFSS) and fiberoptic endoscopic evaluation of swallowing (FEES) at postoperative days 7-15, and classified according to the food intake level scale (FILS). Perioperative swallowing rehabilitation was performed in all cases. RESULTS: In the 187 included patients, the median PMI was 5.42 cm2/m2 for men and 3.43 cm2/m2 for women, and 133 cases (71%) met the sarcopenia criteria. The FILS <4 (no oral intake) was 15% in the non-sarcopenia group, and 38% in the sarcopenia group (P = 0.003). There was no significant difference in the incidence of postoperative complications, including pneumonia and re-admission due to pneumonia, between the two groups. Preoperative sarcopenia and recurrent laryngeal nerve palsy were be independent risk factors for postoperative dysphagia. CONCLUSIONS: Sarcopenic patients with esophageal cancer develop postoperative dysphagia more often than non-sarcopenic patients. Prehabilitation and nutritional support for patients with preoperative sarcopenia could play an important role to mitigate postoperative dysphagia.

Clinical usefulness of sputum culture on the first postoperative day to predict early postoperative pneumonia after esophagectomy for esophageal cancer.

BACKGROUND: Postoperative pneumonia is a serious prognostic problem that can appear after esophagectomy in patients with esophageal cancer. The past reports have considered the usefulness of perioperative culture examinations for predicting postoperative pneumonia; however, the direct relationship between these examinations and postoperative complications remains unclear. METHODS: This study retrospectively analyzed esophageal cancer patients who underwent esophagectomy followed by sputum culture on the first postoperative day. The bacterial species that frequently cause hospital-acquired pneumonia were chosen as the target species in this study. The relationship between culture examination and postoperative pneumonia within one week (7 days) after esophagectomy was investigated. RESULTS: Sputum cultures on the first postoperative day were investigated in 238 patients who underwent esophagectomy for esophageal cancer. Forty-one patients developed pneumonia within one week after surgery. The target bacterial species were detected in 26 of 238 sputum cultures (10.9%). In the univariate analysis, a Brinkman index, detection of target bacterial species, detection of Gram-positive cocci, and Gram-negative rods were significantly associated with postoperative pneumonia. In the three independent multivariate analyses, the target bacterial species, Gram-positive cocci, and Gram-negative rods (p = 0.001, 0.042, and < 0.001) were individually identified as independent risk factors of postoperative pneumonia in addition to a Brinkman index. CONCLUSIONS: Detection of target bacterial species by sputum culture on the first postoperative day after esophagectomy was an independent risk factor of postoperative pneumonia within 7 days after surgery. Prospective studies for the prevention of early postoperative pneumonia using sputum culture on the first postoperative day can be considered.

Mercury bioremediation by mercury resistance transposon-mediated in situ molecular breeding.

Mercury-resistant (HgR) bacteria occur in various bacterial species from a wide variety of environmental sources. Resistance is conferred by a set of operon genes termed the mer operon. Many HgR bacteria have been isolated from diverse environments and clinical samples, and it is recognized that mer operons are often localized on transposons. Previous research reports have suggested that HgR transposons participate in the horizontal gene transfer of mer operons among bacteria. This was confirmed by a study that found that mer operons were distributed worldwide in Bacilli with dissemination of TnMERI1-like transposons. In this mini review, possible strategies for transposon-mediated in situ molecular breeding (ISMoB) of HgR bacteria in their natural habitat are discussed. In ISMoB, the target microorganisms for breeding are indigenous bacteria that are not HgR but that are dominant and robust in their respective environments. Additionally, we propose a new concept of bioremediation technology for environmental mercury pollution by applying transposon-mediated ISMoB for environmental mercury pollution control.

Biodiversity and multifunctionality in a microbial community: a novel theoretical approach to quantify functional redundancy.

Ecosystems have a limited buffering capacity of multiple ecosystem functions against biodiversity loss (i.e. low multifunctional redundancy). We developed a novel theoretical approach to evaluate multifunctional redundancy in a microbial community using the microbial genome database (MBGD) for comparative analysis. In order to fully implement functional information, we defined orthologue richness in a community, each of which is a functionally conservative evolutionary unit in genomes, as an index of community multifunctionality (MF). We constructed a graph of expected orthologue richness in a community (MF) as a function of species richness (SR), fit the power function to SR (i.e. MF = cSR(a)), and interpreted the higher exponent a as the lower multifunctional redundancy. Through a microcosm experiment, we confirmed that MF defined by orthologue richness could predict the actual multiple functions. We simulated random and non-random community assemblages using full genomic data of 478 prokaryotic species in the MBGD, and determined that the exponent in microbial communities ranged from 0.55 to 0.75. This exponent range provided a quantitative estimate that a 6.6-8.9% loss limit in SR occurred in a microbial community for an MF reduction no greater than 5%, suggesting a non-negligible initial loss effect of microbial diversity on MF.

Microbial community composition and function in an urban waterway with combined sewer overflows before and after implementation of a stormwater storage pipe.

When the wastewater volume exceeds the sewer pipe capacity during extreme rainfall events, untreated sewage discharges directly into rivers as combined sewer overflow (CSO). To compare the impacts of CSOs and stormwater on urban waterways, we assessed physicochemical water quality, the 16S rRNA gene-based bacterial community structure, and EcoPlate-based microbial functions during rainfall periods in an urban waterway before and after a stormwater storage pipe was commissioned. A temporal variation analysis showed that CSOs have significant impacts on microbial function and bacterial community structure, while their contributions to physicochemical parameters, bacterial abundance, and chlorophyll a were not confirmed. Heat map analysis showed that the impact of CSO on the waterway bacterial community structure was temporal and the bacterial community composition in CSO is distinct from that in sewers. Hierarchical clustering analysis revealed that the waterway physicochemical water qualities, bacterial community composition, and microbial community function were distinguishable from the upper reach of the river, rather than between CSO and stormwater. Changes in the relative abundance of tetracycline resistance (tet) genes-especially tet(M)-were observed after CSOs but did not coincide with changes in the microbial community composition, suggesting that the parameters affecting the microbial community composition and relative abundance of tet genes differ. After pipe implementation, however, stormwater did not contribute to the abundance of tet genes in the waterway. These results indicate that CSO-induced acute microbial disturbances in the urban waterway were alleviated by the implementation of a stormwater storage pipe and will support the efficiency of storage pipe operation for waterway management in urban areas.