Bacteria are key drivers in regulating ecosystem functions, and understanding the diversity and dynamic changes in bacteria in composting is very important for optimizing compost. This study investigated the structure, composition, and function of bacterial communities in alkaline pig manure compost using Miseq sequencing, PICRUSt2. The ACE and Chao1 indices of the bacterial communities in various phases were significantly different. Bacterial communities of alkaline pig compost were different from neutral and acidic swine manure compost, and there were 438 genera of common bacteria in various stages. The main bacterium was the phylum Firmicutes. There were six genera, including Romboutsia, Clostridium, Terrisporobacter, norank_f_Marinococcaceae, Saccharomonospora, and unclassified_f_Bacillaceae, that were significantly correlated (p < 0.05), or even extremely significantly correlated (p < 0.001), with the physicochemical properties. TOC, moisture, C/N, and Tem were the key factors that caused changes in bacterial communities in composting. PICRUSt2 analysis showed that there were seven functional groups: metabolism (45.02–48.07%), environmental information processing (15.25–16.00%), genetic information processing (16.97–20.02%), cellular processes (3.63–4.37%), human diseases (0.71–0.82%), organismal systems (0.66–0.77%), and unclassified (13.93–14.36%). This study will provide a reference for improving bacteria growth and reproduction conditions in pig manure composting, optimizing the process, and improving the efficiency of composting.

Microbial community diversity, abundance, and activity drive composting by governing organic matter decomposition and nutrient turnover. Despite extensive work, the links between microbial succession and physicochemical dynamics, and the role of microbial co-occurrence patterns, remain poorly understood. This study characterizes the temporal succession of bacterial and fungal communities during aerobic chicken manure composting and relates these changes to key physicochemical indicators. Fresh chicken manure and wheat straw (8:1, v/v) were composted for 35 days, with samples collected at four stages: initial (day 0), thermophilic (day 3), bio-oxidative (day 15), and maturation (day 35). High-throughput sequencing, bioinformatics analyses, and statistical approaches were used to characterize microbial community diversity, structure, and network interactions, and to assess their relationships with temperature, pH, moisture, and nutrient contents. During composting, physicochemical properties changed dynamically. Bacterial community diversity and richness decreased from 391 genera at T1 to 229 at T4, while fungal genera fluctuated, peaking at T1 (565) and reaching a minimum at T4 (379). Firmicutes, Actinobacteria, Ascomycota, and Basidiomycota were the dominant phyla, while Pseudogracilibacillus, Penicillium, and Aspergillus were the predominant genera across stages. Network analysis revealed clear separation and reorganization of microbial communities during composting. The principal drivers for bacterial communities were total nitrogen (TN), ammonium-N (NH4+-N), the carbon-to-nitrogen ratio (C/N), and temperature, whereas for fungal communities the primary influences were pH, nitrate-N (NO3−-N), and total organic carbon (TOC). Collectively, the findings demonstrate that fluctuations in physicochemical conditions steer microbial succession in chicken-manure composting and imply that adjusting key environmental factors and microbial assemblages could enhance compost maturation and final quality.